20921875 has 28 divisors (see below), whose sum is σ = 28437136. Its totient is φ = 15300000.

The previous prime is 20921867. The next prime is 20921897. The reversal of 20921875 is 57812902.

It is not a de Polignac number, because 20921875 - 2³ = 20921867 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20921875.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 203074 + ... + 203176.

It is an arithmetic number, because the mean of its divisors is an integer number (1015612).

Almost surely, 2^20921875 is an apocalyptic number.

20921875 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

20921875 is a deficient number, since it is larger than the sum of its proper divisors (7515261).

20921875 is an frugal number, since it uses more digits than its factorization.

20921875 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146 (or 121 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 20921875 is about 4574.0436158830. The cubic root of 20921875 is about 275.5498639985.

The spelling of 20921875 in words is "twenty million, nine hundred twenty-one thousand, eight hundred seventy-five".