21561025327517 has 16 divisors (see below), whose sum is σ = 24625269415152. Its totient is φ = 18701390991360.

The previous prime is 21561025327511. The next prime is 21561025327579. The reversal of 21561025327517 is 71572352016512.

It can be written as a sum of positive squares in 8 ways, for example, as 5258335127236 + 16302690200281 = 2293106^2 + 4037659^2 .

It is a cyclic number.

It is not a de Polignac number, because 21561025327517 - 2²² = 21561021133213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561025327511) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 78924584 + ... + 79197297.

It is an arithmetic number, because the mean of its divisors is an integer number (1539079338447).

Almost surely, 2^{21561025327517} is an apocalyptic number.

It is an amenable number.

21561025327517 is a deficient number, since it is larger than the sum of its proper divisors (3064244087635).

21561025327517 is a wasteful number, since it uses less digits than its factorization.

21561025327517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158122528.

The product of its (nonzero) digits is 882000, while the sum is 47.

The spelling of 21561025327517 in words is "twenty-one trillion, five hundred sixty-one billion, twenty-five million, three hundred twenty-seven thousand, five hundred seventeen".