81257564 has 6 divisors (see below), whose sum is σ = 142200744. Its totient is φ = 40628780.

The previous prime is 81257557. The next prime is 81257591. The reversal of 81257564 is 46575218.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10157192 + ... + 10157199.

It is an arithmetic number, because the mean of its divisors is an integer number (23700124).

Almost surely, 2^81257564 is an apocalyptic number.

It is an amenable number.

81257564 is a deficient number, since it is larger than the sum of its proper divisors (60943180).

81257564 is a wasteful number, since it uses less digits than its factorization.

81257564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20314395 (or 20314393 counting only the distinct ones).

The product of its digits is 67200, while the sum is 38.

The square root of 81257564 is about 9014.2977541237. The cubic root of 81257564 is about 433.1329927305.

The spelling of 81257564 in words is "eighty-one million, two hundred fifty-seven thousand, five hundred sixty-four".