81634607720 has 32 divisors (see below), whose sum is σ = 183688273800. Its totient is φ = 32651993088.

The previous prime is 81634607657. The next prime is 81634607723. The reversal of 81634607720 is 2770643618.

It can be written as a sum of positive squares in 4 ways, for example, as 17486888644 + 64147719076 = 132238^2 + 253274^2 .

It is not an unprimeable number, because it can be changed into a prime (81634607723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 822536 + ... + 916424.

Almost surely, 2^81634607720 is an apocalyptic number.

It is an amenable number.

81634607720 is an abundant number, since it is smaller than the sum of its proper divisors (102053666080).

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

81634607720 is a wasteful number, since it uses less digits than its factorization.

81634607720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115637 (or 115633 counting only the distinct ones).

The product of its (nonzero) digits is 338688, while the sum is 44.

The spelling of 81634607720 in words is "eighty-one billion, six hundred thirty-four million, six hundred seven thousand, seven hundred twenty".