21357517 has 2 divisors, whose sum is σ = 21357518. Its totient is φ = 21357516.

The previous prime is 21357509. The next prime is 21357529. The reversal of 21357517 is 71575312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18139081 + 3218436 = 4259^2 + 1794^2 .

It is a cyclic number.

It is not a de Polignac number, because 21357517 - 2³ = 21357509 is a prime.

It is a super-2 number, since 2×21357517² = 912287064810578, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21357617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10678758 + 10678759.

It is an arithmetic number, because the mean of its divisors is an integer number (10678759).

Almost surely, 2^21357517 is an apocalyptic number.

It is an amenable number.

21357517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21357517 is an equidigital number, since it uses as much as digits as its factorization.

21357517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7350, while the sum is 31.

The square root of 21357517 is about 4621.4193707129. The cubic root of 21357517 is about 277.4492702765.

The spelling of 21357517 in words is "twenty-one million, three hundred fifty-seven thousand, five hundred seventeen".