20731257 has 12 divisors (see below), whose sum is σ = 31247424. Its totient is φ = 13219800.

The previous prime is 20731253. The next prime is 20731267. The reversal of 20731257 is 75213702.

It is not a de Polignac number, because 20731257 - 2² = 20731253 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20731257.

It is not an unprimeable number, because it can be changed into a prime (20731253) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 49869 + ... + 50282.

It is an arithmetic number, because the mean of its divisors is an integer number (2603952).

Almost surely, 2^20731257 is an apocalyptic number.

It is an amenable number.

20731257 is a deficient number, since it is larger than the sum of its proper divisors (10516167).

20731257 is a wasteful number, since it uses less digits than its factorization.

20731257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100180 (or 100177 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 20731257 is about 4553.1590132566. The cubic root of 20731257 is about 274.7104699348.

Adding to 20731257 its reverse (75213702), we get a palindrome (95944959).

The spelling of 20731257 in words is "twenty million, seven hundred thirty-one thousand, two hundred fifty-seven".