21917513 has 2 divisors, whose sum is σ = 21917514. Its totient is φ = 21917512.

The previous prime is 21917503. The next prime is 21917521. The reversal of 21917513 is 31571912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14227984 + 7689529 = 3772^2 + 2773^2 .

It is a cyclic number.

It is not a de Polignac number, because 21917513 - 2²⁰ = 20868937 is a prime.

It is a super-2 number, since 2×21917513² = 960754752210338, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21917503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10958756 + 10958757.

It is an arithmetic number, because the mean of its divisors is an integer number (10958757).

Almost surely, 2^21917513 is an apocalyptic number.

It is an amenable number.

21917513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21917513 is an equidigital number, since it uses as much as digits as its factorization.

21917513 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1890, while the sum is 29.

The square root of 21917513 is about 4681.6143583170. The cubic root of 21917513 is about 279.8532947462.

The spelling of 21917513 in words is "twenty-one million, nine hundred seventeen thousand, five hundred thirteen".