21997697 has 2 divisors, whose sum is σ = 21997698. Its totient is φ = 21997696.

The previous prime is 21997691. The next prime is 21997709. The reversal of 21997697 is 79679912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12609601 + 9388096 = 3551^2 + 3064^2 .

It is a cyclic number.

It is not a de Polignac number, because 21997697 - 2⁴ = 21997681 is a prime.

It is not a weakly prime, because it can be changed into another prime (21997691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10998848 + 10998849.

It is an arithmetic number, because the mean of its divisors is an integer number (10998849).

Almost surely, 2^21997697 is an apocalyptic number.

It is an amenable number.

21997697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21997697 is an equidigital number, since it uses as much as digits as its factorization.

21997697 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 428652, while the sum is 50.

The square root of 21997697 is about 4690.1702527733. The cubic root of 21997697 is about 280.1941553053.

The spelling of 21997697 in words is "twenty-one million, nine hundred ninety-seven thousand, six hundred ninety-seven".