21938569 has 2 divisors, whose sum is σ = 21938570. Its totient is φ = 21938568.

The previous prime is 21938563. The next prime is 21938591. The reversal of 21938569 is 96583912.

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., 21855625 + 82944 = 4675^2 + 288^2 .

It is a cyclic number.

It is not a de Polignac number, because 21938569 - 2⁹ = 21938057 is a prime.

It is a super-2 number, since 2×21938569² = 962601619535522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21938563) 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, 10969284 + 10969285.

It is an arithmetic number, because the mean of its divisors is an integer number (10969285).

Almost surely, 2^21938569 is an apocalyptic number.

It is an amenable number.

21938569 is a deficient number, since it is larger than the sum of its proper divisors (1).

21938569 is an equidigital number, since it uses as much as digits as its factorization.

21938569 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 21938569 is about 4683.8626154062. The cubic root of 21938569 is about 279.9428837580.

The spelling of 21938569 in words is "twenty-one million, nine hundred thirty-eight thousand, five hundred sixty-nine".