20931577985 has 8 divisors (see below), whose sum is σ = 25461974760. Its totient is φ = 16515874944.

The previous prime is 20931577973. The next prime is 20931577999. The reversal of 20931577985 is 58977513902.

It can be written as a sum of positive squares in 4 ways, for example, as 66064384 + 20865513601 = 8128^2 + 144449^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20931577985 - 2¹² = 20931573889 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20931577985.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28673030 + ... + 28673759.

It is an arithmetic number, because the mean of its divisors is an integer number (3182746845).

Almost surely, 2^20931577985 is an apocalyptic number.

It is an amenable number.

20931577985 is a deficient number, since it is larger than the sum of its proper divisors (4530396775).

20931577985 is an equidigital number, since it uses as much as digits as its factorization.

20931577985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57346867.

The product of its (nonzero) digits is 4762800, while the sum is 56.

The spelling of 20931577985 in words is "twenty billion, nine hundred thirty-one million, five hundred seventy-seven thousand, nine hundred eighty-five".