81556624 has 10 divisors (see below), whose sum is σ = 158015990. Its totient is φ = 40778304.

The previous prime is 81556619. The next prime is 81556639. The reversal of 81556624 is 42665518.

It can be written as a sum of positive squares in only one way, i.e., 72795024 + 8761600 = 8532^2 + 2960^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2548629 + ... + 2548660.

It is an arithmetic number, because the mean of its divisors is an integer number (15801599).

Almost surely, 2^81556624 is an apocalyptic number.

It is an amenable number.

81556624 is a deficient number, since it is larger than the sum of its proper divisors (76459366).

81556624 is a wasteful number, since it uses less digits than its factorization.

81556624 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5097297 (or 5097291 counting only the distinct ones).

The product of its digits is 57600, while the sum is 37.

The square root of 81556624 is about 9030.8706114084. The cubic root of 81556624 is about 433.6637091338.

The spelling of 81556624 in words is "eighty-one million, five hundred fifty-six thousand, six hundred twenty-four".