81391525264 has 135 divisors (see below), whose sum is σ = 192198761643. Its totient is φ = 33290152896.

The previous prime is 81391525247. The next prime is 81391525279. The reversal of 81391525264 is 46252519318.

The square root of 81391525264 is 285292.

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

It is a Harshad number since it is a multiple of its sum of digits (46).

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 183727827 + ... + 183728269.

Almost surely, 2^81391525264 is an apocalyptic number.

81391525264 is the 285292-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81391525264

81391525264 is an abundant number, since it is smaller than the sum of its proper divisors (110807236379).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81391525264 is an equidigital number, since it uses as much as digits as its factorization.

81391525264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 954 (or 475 counting only the distinct ones).

The product of its digits is 518400, while the sum is 46.

The spelling of 81391525264 in words is "eighty-one billion, three hundred ninety-one million, five hundred twenty-five thousand, two hundred sixty-four".