21913237 has 2 divisors, whose sum is σ = 21913238. Its totient is φ = 21913236.

The previous prime is 21913201. The next prime is 21913277. The reversal of 21913237 is 73231912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20439441 + 1473796 = 4521^2 + 1214^2 .

It is a cyclic number.

It is not a de Polignac number, because 21913237 - 2⁷ = 21913109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21913277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10956618 + 10956619.

It is an arithmetic number, because the mean of its divisors is an integer number (10956619).

Almost surely, 2^21913237 is an apocalyptic number.

It is an amenable number.

21913237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21913237 is an equidigital number, since it uses as much as digits as its factorization.

21913237 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2268, while the sum is 28.

The square root of 21913237 is about 4681.1576559650. The cubic root of 21913237 is about 279.8350942245.

It can be divided in two parts, 219 and 13237, that added together give a square (13456 = 116²).

The spelling of 21913237 in words is "twenty-one million, nine hundred thirteen thousand, two hundred thirty-seven".