21249637 has 2 divisors, whose sum is σ = 21249638. Its totient is φ = 21249636.

The previous prime is 21249623. The next prime is 21249671. The reversal of 21249637 is 73694212.

It is an a-pointer prime, because the next prime (21249671) can be obtained adding 21249637 to its sum of digits (34).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19483396 + 1766241 = 4414^2 + 1329^2 .

It is a cyclic number.

It is not a de Polignac number, because 21249637 - 2¹⁵ = 21216869 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21249737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10624818 + 10624819.

It is an arithmetic number, because the mean of its divisors is an integer number (10624819).

Almost surely, 2^21249637 is an apocalyptic number.

It is an amenable number.

21249637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21249637 is an equidigital number, since it uses as much as digits as its factorization.

21249637 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 34.

The square root of 21249637 is about 4609.7328556002. The cubic root of 21249637 is about 276.9813356555.

The spelling of 21249637 in words is "twenty-one million, two hundred forty-nine thousand, six hundred thirty-seven".