81565776 has 30 divisors (see below), whose sum is σ = 228271290. Its totient is φ = 27188544.

The previous prime is 81565763. The next prime is 81565787. The reversal of 81565776 is 67756518.

81565776 is a `hidden beast` number, since 81 + 565 + 7 + 7 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 75690000 + 5875776 = 8700^2 + 2424^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 283071 + ... + 283358.

It is an arithmetic number, because the mean of its divisors is an integer number (7609043).

Almost surely, 2^81565776 is an apocalyptic number.

It is an amenable number.

81565776 is an abundant number, since it is smaller than the sum of its proper divisors (146705514).

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

81565776 is a wasteful number, since it uses less digits than its factorization.

81565776 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 566443 (or 566434 counting only the distinct ones).

The product of its digits is 352800, while the sum is 45.

The square root of 81565776 is about 9031.3773036010. The cubic root of 81565776 is about 433.6799299369.

The spelling of 81565776 in words is "eighty-one million, five hundred sixty-five thousand, seven hundred seventy-six".