21252137 has 2 divisors, whose sum is σ = 21252138. Its totient is φ = 21252136.

The previous prime is 21252113. The next prime is 21252139. The reversal of 21252137 is 73125212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11417641 + 9834496 = 3379^2 + 3136^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21252137 is a prime.

Together with 21252139, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21252139) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10626068 + 10626069.

It is an arithmetic number, because the mean of its divisors is an integer number (10626069).

Almost surely, 2^21252137 is an apocalyptic number.

It is an amenable number.

21252137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21252137 is an equidigital number, since it uses as much as digits as its factorization.

21252137 is an evil number, because the sum of its binary digits is even.

The product of its digits is 840, while the sum is 23.

The square root of 21252137 is about 4610.0040130134. The cubic root of 21252137 is about 276.9921974282.

Adding to 21252137 its reverse (73125212), we get a palindrome (94377349).

The spelling of 21252137 in words is "twenty-one million, two hundred fifty-two thousand, one hundred thirty-seven".