81712564 has 6 divisors (see below), whose sum is σ = 142996994. Its totient is φ = 40856280.

The previous prime is 81712541. The next prime is 81712567. The reversal of 81712564 is 46521718.

It can be written as a sum of positive squares in only one way, i.e., 76422564 + 5290000 = 8742^2 + 2300^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81712567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10214067 + ... + 10214074.

Almost surely, 2^81712564 is an apocalyptic number.

It is an amenable number.

81712564 is a deficient number, since it is larger than the sum of its proper divisors (61284430).

81712564 is a wasteful number, since it uses less digits than its factorization.

81712564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20428145 (or 20428143 counting only the distinct ones).

The product of its digits is 13440, while the sum is 34.

The square root of 81712564 is about 9039.5002074230. The cubic root of 81712564 is about 433.9399281180.

The spelling of 81712564 in words is "eighty-one million, seven hundred twelve thousand, five hundred sixty-four".