21036637 has 2 divisors, whose sum is σ = 21036638. Its totient is φ = 21036636.

The previous prime is 21036623. The next prime is 21036647. The reversal of 21036637 is 73663012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20985561 + 51076 = 4581^2 + 226^2 .

It is a cyclic number.

It is not a de Polignac number, because 21036637 - 2¹⁵ = 21003869 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21036647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10518318 + 10518319.

It is an arithmetic number, because the mean of its divisors is an integer number (10518319).

Almost surely, 2^21036637 is an apocalyptic number.

It is an amenable number.

21036637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21036637 is an equidigital number, since it uses as much as digits as its factorization.

21036637 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 28.

The square root of 21036637 is about 4586.5713774016. The cubic root of 21036637 is about 276.0527668138.

Adding to 21036637 its reverse (73663012), we get a palindrome (94699649).

The spelling of 21036637 in words is "twenty-one million, thirty-six thousand, six hundred thirty-seven".