My Hundred Friends

My Hundred Friends is an illustrated hardcover book for children ages 7-11 or for anyone learning about factors, multiples, and primes. The story makes lighthearted connections to family, sports, history, and science. Readers meet jellybean-shaped number-characters in their cozy world where math patterns, sequences, and combinations form friendships.

Questions? Author requests? Contact us!

PREORDER the book here – release planned for November 2026

The book is in the making! You will receive your book when it comes out. We will send you periodic updates by email and notify you when it’s released.

Shipping will be added at checkout. We ship books worldwide.

70% of Natural Math book royalties go to the book authors.

Campaign updates

Boost and Encourage

Every math friend is welcome. Send the author an encouraging note and get the PDF of My Hundred Friends to delight your children or students at the price you type into the window below.

PREORDER eBook – $8

You will receive the Kindle, iOS, and PDF My Hundred Friends eBooks. The files will be DRM-free.

PREORDER Beautiful Hardcover – $25

You will receive one hardcover My Hundred Friends book and eBooks.

PREORDER Poster – $25

You will receive a 12-by-18-inch glossy wall poster with all 100 number friends in their factorization diagram form, along with eBooks of My Hundred Friends.

Big discounts for small bundles – with any titles

Mathematics works so much better with others! Mix and match any number of posters and books in your shopping cart to make your own bundles. Get a bundle together with friends, treat your math circle, bring books as camp or event gifts, or bring your family a mini-library of joyful mathematics. You save on shipping and also book prices: $3 off each book for 2-4 books and $6 off each book for 5 or more books.

eBook discount is $3 off each eBook when you buy two or more.
Add the books to your cart. The discounts will apply automatically.

This is our crowdfunding campaign video. Big thanks to the 84 campaign backers who made the book possible!

Author’s Note

The origin of this story came to me about a week before my 48th birthday. As my birthday approached, I thought about my upcoming new age: “48… 48… That’s 16 times 3. Oh, that’s cool; I’ve lived through three 16-year-long eras.” I do this every year on my birthday. I wonder, “Is my age a prime number? Is my age a perfect square? How does my age factor?” And so on. As I thought about this, I realized that I have a genuine relationship with these numbers. And I wondered if I could share this relationship with numbers with others by writing this story.

I relate to numbers in symbolic and personal ways. This is an example of a symbolic relationship: 7 days is one week. This is an example of a personal relationship: Growing up, there were 3 kids in my family, so 3 is Kyle, Kevin, and Kara, my two brothers and me. These connections invite the reader to think about their own relationships to the numbers 1 to 100.

Author’s sketch of page 3

The story is bursting with adorable number-characters. They romp around, visiting one another’s pages and adding a lighthearted tone to the story. A 6th-grade reader said, “The drawings are so cute, so sweet!” Meanwhile, a mathematician will recognize friendly pathways into sequences and series, combinatorics, and number theory.

My Hundred Friends has a repetitiveness and rhythm that readers find satisfying. There are many patterns in the book, patterns like “Look! It’s me and me again!” As the patterns occur again and again, readers start to anticipate them, making predictions and feeling contentment when the patterns play out as predicted. A student reader said, “I like the patterns in the book. I feel rewarded.”

Illustrated page 9

All good relationships grow over time. My Hundred Friends offers an exploration of factors and primes so active and tactile that you can almost dive into the play. While the colors in the story form a mathematical structure, the number-characters’ visits to one another also form a web of social connections. With bright, vivid colors and joyful playdates, the number-characters help readers see and feel what it means to factor a number into its prime factorization.

Readers develop number sense by spending time with and rollicking along with the number-characters. The book shows how any number can make friends with any other number, whatever their colors or stripes. Readers: What number connections and number patterns might you make? How might you pretend-play with your favorite number-characters?

Kara’s sketchbook

I’m good friends with the numbers 1 to 100. My sincere hope is that readers will develop more friendly connections with the number-characters and, by extension, with the numbers themselves. The book is a kind, welcoming math gathering: I invite you to come, hang out, and meet a few new friends.

Number Relationships? Why?

By exploring the numbers through relationships to things in our lives, we show children that they can make their own personal connections to numbers. By exploring the numbers as playful, quirky number-characters, we hope readers develop friendly connections with the number-characters and then, with the numbers. By exploring the number-characters’ relationships to one another, we show that multiplication creates a web of relationships.

Illustrated page 12

Reading our favorite stories, if we care about a character, we connect and build a relationship with them. We believe that math and relationships are complementary tools for building human understanding and connecting essential ideas. We believe that every child has number relationships to explore.

Meet the Author

Kara Shane Colley is a math educator. She has taught middle school, high school, and community college math in the Marshall Islands, upstate New York, England, and Oregon. Kara has led math circles and math teacher circles. Currently, she works as a math curriculum writer.

Reading is a huge part of her life. Kara loves to read novels, newspapers (the kind printed on actual paper and delivered to your doorstep), and Supreme Court decisions. She is an advocate for public spaces, especially for city parks and public libraries. She is also a figure skater, an open water swimmer, a wilderness backpacker, a shape note singer, and a fiddle player. Kara lives in Portland, Oregon, with her sweetie, Sky, and her two kids. This is her first book.

Meet the Illustrator

Coley Nielsen is a children’s book illustrator living in Portland, Oregon. She works in traditional and digital media, always seeking a warm, textural, hand-done quality in her art. She finds joy in creating silly, memorable characters and cozy, colorful worlds.

Meet the Publisher

At the Natural Math Alliance, we believe that a good world is possible with better mathematics. Together with children, parents, teachers, and organizers, we help everyone grow a happy familiarity with all sixty-plus mathematics subjects as math makers. To match these goals, we developed a unique publishing process, giving authors, artists, and even readers a lot of creative control.

A book starts with amazing authors who deeply care about mathematics and learning. Each author spends many hours improving every aspect of the manuscript by testing the book with children, families, and classes.

Next comes our Future Book Club: the brave volunteers who field-test the draft in their own families, classes, math circles, book clubs, museum groups, and other programs. They come from all learning backgrounds and all continents (except Antarctica, so far), making Natural Math books more community-responsive and real.

Crowdfunding comes next. Thank you!

Our crew of professional editors, proofreaders, and designers is paid with the crowdfunding money. They make the book a joy to hold, each page or eBook screen a smooth reading experience. Natural Math books are distributed by the American Mathematical Society and have been featured by The Atlantic, The NY Times, and many lovely press and online places dedicated to learning, parenting, and mathematics.

As with all our previous books, My Hundred Friends will be published under a Creative Commons license. That means that people all over the world will be able to access its content, translate it into different languages—and share their ideas based on the book. The Creative Commons site features an interview with the Natural Math founder in its celebration of innovative projects in education.

If you are a part of the Natural Math community, thank you for your continuing support. If you are new to Natural Math, welcome to the adventure!

$Natural Math book covers as of October 2025$