81555856 has 10 divisors (see below), whose sum is σ = 158014502. Its totient is φ = 40777920.

The previous prime is 81555839. The next prime is 81555869. The reversal of 81555856 is 65855518.

It can be written as a sum of positive squares in only one way, i.e., 70560000 + 10995856 = 8400^2 + 3316^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2548605 + ... + 2548636.

Almost surely, 2^81555856 is an apocalyptic number.

It is an amenable number.

81555856 is a deficient number, since it is larger than the sum of its proper divisors (76458646).

81555856 is a wasteful number, since it uses less digits than its factorization.

81555856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5097249 (or 5097243 counting only the distinct ones).

The product of its digits is 240000, while the sum is 43.

The square root of 81555856 is about 9030.8280904909. The cubic root of 81555856 is about 433.6623478924.

The spelling of 81555856 in words is "eighty-one million, five hundred fifty-five thousand, eight hundred fifty-six".