21637697 has 2 divisors, whose sum is σ = 21637698. Its totient is φ = 21637696.

The previous prime is 21637673. The next prime is 21637739. The reversal of 21637697 is 79673612.

21637697 is nontrivially palindromic in base 16.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17673616 + 3964081 = 4204^2 + 1991^2 .

It is a cyclic number.

It is not a de Polignac number, because 21637697 - 2⁶ = 21637633 is a prime.

It is not a weakly prime, because it can be changed into another prime (21637607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10818848 + 10818849.

It is an arithmetic number, because the mean of its divisors is an integer number (10818849).

Almost surely, 2^21637697 is an apocalyptic number.

It is an amenable number.

21637697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21637697 is an equidigital number, since it uses as much as digits as its factorization.

21637697 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 95256, while the sum is 41.

The square root of 21637697 is about 4651.6337990001. The cubic root of 21637697 is about 278.6572487971.

The spelling of 21637697 in words is "twenty-one million, six hundred thirty-seven thousand, six hundred ninety-seven".