21593657 has 2 divisors, whose sum is σ = 21593658. Its totient is φ = 21593656.

The previous prime is 21593653. The next prime is 21593659. The reversal of 21593657 is 75639512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14776336 + 6817321 = 3844^2 + 2611^2 .

It is a cyclic number.

It is not a de Polignac number, because 21593657 - 2² = 21593653 is a prime.

Together with 21593659, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21593657.

It is not a weakly prime, because it can be changed into another prime (21593653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10796828 + 10796829.

It is an arithmetic number, because the mean of its divisors is an integer number (10796829).

Almost surely, 2^21593657 is an apocalyptic number.

It is an amenable number.

21593657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21593657 is an equidigital number, since it uses as much as digits as its factorization.

21593657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56700, while the sum is 38.

The square root of 21593657 is about 4646.8975671947. The cubic root of 21593657 is about 278.4680666090.

The spelling of 21593657 in words is "twenty-one million, five hundred ninety-three thousand, six hundred fifty-seven".