21237157 has 2 divisors, whose sum is σ = 21237158. Its totient is φ = 21237156.

The previous prime is 21237143. The next prime is 21237173. The reversal of 21237157 is 75173212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10797796 + 10439361 = 3286^2 + 3231^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21237157 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21237187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10618578 + 10618579.

It is an arithmetic number, because the mean of its divisors is an integer number (10618579).

Almost surely, 2^21237157 is an apocalyptic number.

It is an amenable number.

21237157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21237157 is an equidigital number, since it uses as much as digits as its factorization.

21237157 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2940, while the sum is 28.

The square root of 21237157 is about 4608.3789991710. The cubic root of 21237157 is about 276.9271009407.

The spelling of 21237157 in words is "twenty-one million, two hundred thirty-seven thousand, one hundred fifty-seven".