21005565546431 has 16 divisors (see below), whose sum is σ = 21275511379200. Its totient is φ = 20736900581760.

The previous prime is 21005565546421. The next prime is 21005565546451. The reversal of 21005565546431 is 13464556550012.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21005565546431 is a prime.

It is a super-2 number, since 2×21005565546431² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005565546421) 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, 514204295 + ... + 514245143.

It is an arithmetic number, because the mean of its divisors is an integer number (1329719461200).

Almost surely, 2^{21005565546431} is an apocalyptic number.

21005565546431 is a deficient number, since it is larger than the sum of its proper divisors (269945832769).

21005565546431 is a wasteful number, since it uses less digits than its factorization.

21005565546431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56366.

The product of its (nonzero) digits is 2160000, while the sum is 47.

The spelling of 21005565546431 in words is "twenty-one trillion, five billion, five hundred sixty-five million, five hundred forty-six thousand, four hundred thirty-one".