20931657 has 4 divisors (see below), whose sum is σ = 27908880. Its totient is φ = 13954436.

The previous prime is 20931629. The next prime is 20931667. The reversal of 20931657 is 75613902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20931657 - 2⁸ = 20931401 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20931667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3488607 + ... + 3488612.

It is an arithmetic number, because the mean of its divisors is an integer number (6977220).

Almost surely, 2^20931657 is an apocalyptic number.

It is an amenable number.

20931657 is a deficient number, since it is larger than the sum of its proper divisors (6977223).

20931657 is an equidigital number, since it uses as much as digits as its factorization.

20931657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6977222.

The product of its (nonzero) digits is 11340, while the sum is 33.

The square root of 20931657 is about 4575.1127854950. The cubic root of 20931657 is about 275.5928016542.

The spelling of 20931657 in words is "twenty million, nine hundred thirty-one thousand, six hundred fifty-seven".