20731157 has 4 divisors (see below), whose sum is σ = 21399936. Its totient is φ = 20062380.

The previous prime is 20731153. The next prime is 20731163. The reversal of 20731157 is 75113702.

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 20731157 - 2² = 20731153 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20731153) 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, 334343 + ... + 334404.

It is an arithmetic number, because the mean of its divisors is an integer number (5349984).

Almost surely, 2^20731157 is an apocalyptic number.

It is an amenable number.

20731157 is a deficient number, since it is larger than the sum of its proper divisors (668779).

20731157 is an equidigital number, since it uses as much as digits as its factorization.

20731157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 668778.

The product of its (nonzero) digits is 1470, while the sum is 26.

The square root of 20731157 is about 4553.1480318566. The cubic root of 20731157 is about 274.7100282331.

Adding to 20731157 its reverse (75113702), we get a palindrome (95844859).

The spelling of 20731157 in words is "twenty million, seven hundred thirty-one thousand, one hundred fifty-seven".