81164591236 has 27 divisors (see below), whose sum is σ = 143008824357. Its totient is φ = 40306803120.

The previous prime is 81164591171. The next prime is 81164591239. The reversal of 81164591236 is 63219546118.

The square root of 81164591236 is 284894.

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

It can be written as a sum of positive squares in only one way, i.e., 894368836 + 80270222400 = 29906^2 + 283320^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81164591239) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 103131235 + ... + 103132021.

Almost surely, 2^81164591236 is an apocalyptic number.

81164591236 is the 284894-th square number.

It is an amenable number.

81164591236 is a deficient number, since it is larger than the sum of its proper divisors (61844233121).

81164591236 is an frugal number, since it uses more digits than its factorization.

81164591236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1940 (or 970 counting only the distinct ones).

The product of its digits is 311040, while the sum is 46.

It can be divided in two parts, 81164 and 591236, that added together give a square (672400 = 820²).

The spelling of 81164591236 in words is "eighty-one billion, one hundred sixty-four million, five hundred ninety-one thousand, two hundred thirty-six".