21659657 has 2 divisors, whose sum is σ = 21659658. Its totient is φ = 21659656.

The previous prime is 21659641. The next prime is 21659699. The reversal of 21659657 is 75695612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13388281 + 8271376 = 3659^2 + 2876^2 .

It is a cyclic number.

It is not a de Polignac number, because 21659657 - 2⁴ = 21659641 is a prime.

It is not a weakly prime, because it can be changed into another prime (21659257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10829828 + 10829829.

It is an arithmetic number, because the mean of its divisors is an integer number (10829829).

Almost surely, 2^21659657 is an apocalyptic number.

It is an amenable number.

21659657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21659657 is an equidigital number, since it uses as much as digits as its factorization.

21659657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 113400, while the sum is 41.

The square root of 21659657 is about 4653.9936613622. The cubic root of 21659657 is about 278.7514862476.

The spelling of 21659657 in words is "twenty-one million, six hundred fifty-nine thousand, six hundred fifty-seven".