21897397 has 2 divisors, whose sum is σ = 21897398. Its totient is φ = 21897396.

The previous prime is 21897391. The next prime is 21897431. The reversal of 21897397 is 79379812.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21893041 + 4356 = 4679^2 + 66^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21897397 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21897391) 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, 10948698 + 10948699.

It is an arithmetic number, because the mean of its divisors is an integer number (10948699).

Almost surely, 2^21897397 is an apocalyptic number.

It is an amenable number.

21897397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21897397 is an equidigital number, since it uses as much as digits as its factorization.

21897397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 190512, while the sum is 46.

The square root of 21897397 is about 4679.4654609261. The cubic root of 21897397 is about 279.7676516348.

The spelling of 21897397 in words is "twenty-one million, eight hundred ninety-seven thousand, three hundred ninety-seven".