# 217 (number)

 ← 216 217 218 →
Cardinal two hundred seventeen
Ordinal 217th
(two hundred seventeenth)
Factorization 7 × 31
Greek numeral ΣΙΖ´
Roman numeral CCXVII
Binary 110110012
Ternary 220013
Quaternary 31214
Quinary 13325
Senary 10016
Octal 3318
Duodecimal 16112
217 is a centered hexagonal number, a 12-gonal number, a centered 36-gonal number, a Fermat pseudoprime to base 5, and a Blum integer.[1] It is both the sum of two positive cubes and the difference of two positive consecutive cubes in exactly one way: ${\displaystyle 217=6^{3}+1^{3}=9^{3}-8^{3}}$. When written in binary, it is a non-repetitive Kaprekar number.[2] It is also the sum of all the divisors of 100.