20856644875 has 16 divisors (see below), whose sum is σ = 28395375840. Its totient is φ = 15168468000.

The previous prime is 20856644873. The next prime is 20856644903. The reversal of 20856644875 is 57844665802.

It is not a de Polignac number, because 20856644875 - 2¹ = 20856644873 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (55).

It is not an unprimeable number, because it can be changed into a prime (20856644873) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 7582860 + ... + 7585609.

It is an arithmetic number, because the mean of its divisors is an integer number (1774710990).

Almost surely, 2^20856644875 is an apocalyptic number.

20856644875 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

20856644875 is a deficient number, since it is larger than the sum of its proper divisors (7538730965).

20856644875 is a wasteful number, since it uses less digits than its factorization.

20856644875 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15168495 (or 15168485 counting only the distinct ones).

The product of its (nonzero) digits is 12902400, while the sum is 55.

The spelling of 20856644875 in words is "twenty billion, eight hundred fifty-six million, six hundred forty-four thousand, eight hundred seventy-five".