21573642317 has 2 divisors, whose sum is σ = 21573642318. Its totient is φ = 21573642316.

The previous prime is 21573642289. The next prime is 21573642361. The reversal of 21573642317 is 71324637512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21260847721 + 312794596 = 145811^2 + 17686^2 .

It is a cyclic number.

It is not a de Polignac number, because 21573642317 - 2²⁰ = 21572593741 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21573642367) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10786821158 + 10786821159.

It is an arithmetic number, because the mean of its divisors is an integer number (10786821159).

Almost surely, 2^21573642317 is an apocalyptic number.

It is an amenable number.

21573642317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21573642317 is an equidigital number, since it uses as much as digits as its factorization.

21573642317 is an evil number, because the sum of its binary digits is even.

The product of its digits is 211680, while the sum is 41.

The spelling of 21573642317 in words is "twenty-one billion, five hundred seventy-three million, six hundred forty-two thousand, three hundred seventeen".