20157931 has 4 divisors (see below), whose sum is σ = 20179264. Its totient is φ = 20136600.

The previous prime is 20157923. The next prime is 20157941. The reversal of 20157931 is 13975102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13975102 = 2 ⋅6987551.

It is a cyclic number.

It is not a de Polignac number, because 20157931 - 2³ = 20157923 is a prime.

It is a super-2 number, since 2×20157931² = 812684364401522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20157931.

It is not an unprimeable number, because it can be changed into a prime (20157911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9180 + ... + 11161.

It is an arithmetic number, because the mean of its divisors is an integer number (5044816).

Almost surely, 2^20157931 is an apocalyptic number.

20157931 is a deficient number, since it is larger than the sum of its proper divisors (21333).

20157931 is an equidigital number, since it uses as much as digits as its factorization.

20157931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21332.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 20157931 is about 4489.7584567547. The cubic root of 20157931 is about 272.1543736936.

The spelling of 20157931 in words is "twenty million, one hundred fifty-seven thousand, nine hundred thirty-one".