Everyone that purchases the Off-Kilta Matilda Book is automatically eligible to join The Prime Number Club™. Simply enter the Certificate Number that came with your book in the Coupon Code box below. If you have not purchased the Book, you can directly purchase access to The Prime Number Club™ for $12. Come on in and join the club - we have free STEM guides and teaching activities.

If you have already purchased an Off-Kilta Matilda Book, enter your book number in the coupon section below and click "Apply".

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