81721364960169 has 135 divisors (see below), whose sum is σ = 135437722693581. Its totient is φ = 49069772634960.

The previous prime is 81721364960149. The next prime is 81721364960237. The reversal of 81721364960169 is 96106946312718.

The square root of 81721364960169 is 9039987.

It is a perfect power (a square), and thus also a powerful number.

81721364960169 is a `hidden beast` number, since 8 + 1 + 7 + 2 + 13 + 6 + 4 + 9 + 601 + 6 + 9 = 666.

It is not a de Polignac number, because 81721364960169 - 2²⁵ = 81721331405737 is a prime.

It is a super-2 number, since 2×81721364960169² (a number of 29 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81721364960149) by changing a digit.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 113659756192 + ... + 113659756910.

Almost surely, 2^{81721364960169} is an apocalyptic number.

81721364960169 is the 9039987-th square number.

81721364960169 is the 4519994-th centered octagonal number.

It is an amenable number.

81721364960169 is a deficient number, since it is larger than the sum of its proper divisors (53716357733412).

81721364960169 is an frugal number, since it uses more digits than its factorization.

81721364960169 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1726 (or 860 counting only the distinct ones).

The product of its (nonzero) digits is 23514624, while the sum is 63.

The spelling of 81721364960169 in words is "eighty-one trillion, seven hundred twenty-one billion, three hundred sixty-four million, nine hundred sixty thousand, one hundred sixty-nine".