81778568 has 16 divisors (see below), whose sum is σ = 162354780. Its totient is φ = 38483968.

The previous prime is 81778553. The next prime is 81778607. The reversal of 81778568 is 86587718.

It can be written as a sum of positive squares in 2 ways, for example, as 66552964 + 15225604 = 8158^2 + 3902^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 300521 + ... + 300792.

Almost surely, 2^81778568 is an apocalyptic number.

It is an amenable number.

81778568 is a deficient number, since it is larger than the sum of its proper divisors (80576212).

81778568 is a wasteful number, since it uses less digits than its factorization.

81778568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 601336 (or 601332 counting only the distinct ones).

The product of its digits is 752640, while the sum is 50.

The square root of 81778568 is about 9043.1503360278. The cubic root of 81778568 is about 434.0567361958.

The spelling of 81778568 in words is "eighty-one million, seven hundred seventy-eight thousand, five hundred sixty-eight".