81137620 has 24 divisors (see below), whose sum is σ = 170843400. Its totient is φ = 32368512.

The previous prime is 81137611. The next prime is 81137653. The reversal of 81137620 is 2673118.

It can be written as a sum of positive squares in 4 ways, for example, as 20484676 + 60652944 = 4526^2 + 7788^2 .

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, 2566 + ... + 12994.

It is an arithmetic number, because the mean of its divisors is an integer number (7118475).

Almost surely, 2^81137620 is an apocalyptic number.

It is an amenable number.

81137620 is an abundant number, since it is smaller than the sum of its proper divisors (89705780).

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

81137620 is a wasteful number, since it uses less digits than its factorization.

81137620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10827 (or 10825 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 81137620 is about 9007.6423108381. The cubic root of 81137620 is about 432.9197724303.

The spelling of 81137620 in words is "eighty-one million, one hundred thirty-seven thousand, six hundred twenty".