81511764 has 24 divisors (see below), whose sum is σ = 190639680. Its totient is φ = 27106944.

The previous prime is 81511757. The next prime is 81511819. The reversal of 81511764 is 46711518.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2469 + ... + 13004.

It is an arithmetic number, because the mean of its divisors is an integer number (7943320).

Almost surely, 2^81511764 is an apocalyptic number.

It is an amenable number.

81511764 is an abundant number, since it is smaller than the sum of its proper divisors (109127916).

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

81511764 is a wasteful number, since it uses less digits than its factorization.

81511764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15919 (or 15917 counting only the distinct ones).

The product of its digits is 6720, while the sum is 33.

The square root of 81511764 is about 9028.3865668236. The cubic root of 81511764 is about 433.5841827016.

The spelling of 81511764 in words is "eighty-one million, five hundred eleven thousand, seven hundred sixty-four".