21585840517 has 2 divisors, whose sum is σ = 21585840518. Its totient is φ = 21585840516.

The previous prime is 21585840499. The next prime is 21585840527. The reversal of 21585840517 is 71504858512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20876204196 + 709636321 = 144486^2 + 26639^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21585840517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21585840527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10792920258 + 10792920259.

It is an arithmetic number, because the mean of its divisors is an integer number (10792920259).

Almost surely, 2^21585840517 is an apocalyptic number.

It is an amenable number.

21585840517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21585840517 is an equidigital number, since it uses as much as digits as its factorization.

21585840517 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448000, while the sum is 46.

The spelling of 21585840517 in words is "twenty-one billion, five hundred eighty-five million, eight hundred forty thousand, five hundred seventeen".