81989790 has 16 divisors (see below), whose sum is σ = 196775568. Its totient is φ = 21863936.

The previous prime is 81989771. The next prime is 81989801. The reversal of 81989790 is 9798918.

It is a congruent number.

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, 1366467 + ... + 1366526.

It is an arithmetic number, because the mean of its divisors is an integer number (12298473).

Almost surely, 2^81989790 is an apocalyptic number.

81989790 is an abundant number, since it is smaller than the sum of its proper divisors (114785778).

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

81989790 is a wasteful number, since it uses less digits than its factorization.

81989790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2733003.

The product of its (nonzero) digits is 326592, while the sum is 51.

The square root of 81989790 is about 9054.8213676472. The cubic root of 81989790 is about 434.4301164642.

It can be divided in two parts, 819 and 89790, that added together give a palindrome (90609).

The spelling of 81989790 in words is "eighty-one million, nine hundred eighty-nine thousand, seven hundred ninety".