81710621 has 16 divisors (see below), whose sum is σ = 88957440. Its totient is φ = 74798640.

The previous prime is 81710611. The next prime is 81710647. The reversal of 81710621 is 12601718.

It is a cyclic number.

It is not a de Polignac number, because 81710621 - 2²² = 77516317 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81710611) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 83666 + ... + 84636.

It is an arithmetic number, because the mean of its divisors is an integer number (5559840).

Almost surely, 2^81710621 is an apocalyptic number.

It is an amenable number.

81710621 is a deficient number, since it is larger than the sum of its proper divisors (7246819).

81710621 is a wasteful number, since it uses less digits than its factorization.

81710621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1136.

The product of its (nonzero) digits is 672, while the sum is 26.

The square root of 81710621 is about 9039.3927340281. The cubic root of 81710621 is about 433.9364886144.

The spelling of 81710621 in words is "eighty-one million, seven hundred ten thousand, six hundred twenty-one".