81639570 has 16 divisors (see below), whose sum is σ = 195935040. Its totient is φ = 21770544.

The previous prime is 81639527. The next prime is 81639587. The reversal of 81639570 is 7593618.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1360630 + ... + 1360689.

It is an arithmetic number, because the mean of its divisors is an integer number (12245940).

Almost surely, 2^81639570 is an apocalyptic number.

81639570 is an abundant number, since it is smaller than the sum of its proper divisors (114295470).

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

81639570 is a wasteful number, since it uses less digits than its factorization.

81639570 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2721329.

The product of its (nonzero) digits is 45360, while the sum is 39.

The square root of 81639570 is about 9035.4618033612. The cubic root of 81639570 is about 433.8106764826.

The spelling of 81639570 in words is "eighty-one million, six hundred thirty-nine thousand, five hundred seventy".