81565978 has 16 divisors (see below), whose sum is σ = 132120576. Its totient is φ = 37542960.

The previous prime is 81565961. The next prime is 81565987. The reversal of 81565978 is 87956518.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5863 + ... + 14053.

It is an arithmetic number, because the mean of its divisors is an integer number (8257536).

Almost surely, 2^81565978 is an apocalyptic number.

81565978 is a deficient number, since it is larger than the sum of its proper divisors (50554598).

81565978 is a wasteful number, since it uses less digits than its factorization.

81565978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8589.

The product of its digits is 604800, while the sum is 49.

The square root of 81565978 is about 9031.3884868275. The cubic root of 81565978 is about 433.6802879436.

The spelling of 81565978 in words is "eighty-one million, five hundred sixty-five thousand, nine hundred seventy-eight".