21398569 has 2 divisors, whose sum is σ = 21398570. Its totient is φ = 21398568.

The previous prime is 21398561. The next prime is 21398581. The reversal of 21398569 is 96589312.

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., 20820969 + 577600 = 4563^2 + 760^2 .

It is a cyclic number.

It is not a de Polignac number, because 21398569 - 2³ = 21398561 is a prime.

It is a super-2 number, since 2×21398569² = 915797510495522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21398561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699284 + 10699285.

It is an arithmetic number, because the mean of its divisors is an integer number (10699285).

Almost surely, 2^21398569 is an apocalyptic number.

It is an amenable number.

21398569 is a deficient number, since it is larger than the sum of its proper divisors (1).

21398569 is an equidigital number, since it uses as much as digits as its factorization.

21398569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 116640, while the sum is 43.

The square root of 21398569 is about 4625.8587310898. The cubic root of 21398569 is about 277.6269213524.

The spelling of 21398569 in words is "twenty-one million, three hundred ninety-eight thousand, five hundred sixty-nine".