81587720 has 32 divisors (see below), whose sum is σ = 186093720. Its totient is φ = 32186880.

The previous prime is 81587713. The next prime is 81587731. The reversal of 81587720 is 2778518.

It can be written as a sum of positive squares in 4 ways, for example, as 67010596 + 14577124 = 8186^2 + 3818^2 .

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, 11051 + ... + 16890.

Almost surely, 2^81587720 is an apocalyptic number.

It is an amenable number.

81587720 is an abundant number, since it is smaller than the sum of its proper divisors (104506000).

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

81587720 is a wasteful number, since it uses less digits than its factorization.

81587720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28025 (or 28021 counting only the distinct ones).

The product of its (nonzero) digits is 31360, while the sum is 38.

The square root of 81587720 is about 9032.5920975100. The cubic root of 81587720 is about 433.7188180570.

The spelling of 81587720 in words is "eighty-one million, five hundred eighty-seven thousand, seven hundred twenty".