81757807621 has 16 divisors (see below), whose sum is σ = 93695979520. Its totient is φ = 69884512560.

The previous prime is 81757807613. The next prime is 81757807631. The reversal of 81757807621 is 12670875718.

It is a cyclic number.

It is not a de Polignac number, because 81757807621 - 2³ = 81757807613 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 (81757807631) 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, 4143040 + ... + 4162726.

It is an arithmetic number, because the mean of its divisors is an integer number (5855998720).

Almost surely, 2^81757807621 is an apocalyptic number.

It is an amenable number.

81757807621 is a deficient number, since it is larger than the sum of its proper divisors (11938171899).

81757807621 is a wasteful number, since it uses less digits than its factorization.

81757807621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21304.

The product of its (nonzero) digits is 1317120, while the sum is 52.

The spelling of 81757807621 in words is "eighty-one billion, seven hundred fifty-seven million, eight hundred seven thousand, six hundred twenty-one".