21659969 has 2 divisors, whose sum is σ = 21659970. Its totient is φ = 21659968.

The previous prime is 21659947. The next prime is 21659993. The reversal of 21659969 is 96995612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14440000 + 7219969 = 3800^2 + 2687^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21659969 is a prime.

It is a super-2 number, since 2×21659969² = 938308514161922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21659999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10829984 + 10829985.

It is an arithmetic number, because the mean of its divisors is an integer number (10829985).

Almost surely, 2^21659969 is an apocalyptic number.

It is an amenable number.

21659969 is a deficient number, since it is larger than the sum of its proper divisors (1).

21659969 is an equidigital number, since it uses as much as digits as its factorization.

21659969 is an evil number, because the sum of its binary digits is even.

The product of its digits is 262440, while the sum is 47.

The square root of 21659969 is about 4654.0271808403. The cubic root of 21659969 is about 278.7528246813.

The spelling of 21659969 in words is "twenty-one million, six hundred fifty-nine thousand, nine hundred sixty-nine".