21351431663523 has 48 divisors (see below), whose sum is σ = 33538639680000. Its totient is φ = 13011266165184.

The previous prime is 21351431663483. The next prime is 21351431663533. The reversal of 21351431663523 is 32536613415312.

21351431663523 is a `hidden beast` number, since 2 + 1 + 3 + 5 + 1 + 4 + 3 + 1 + 6 + 635 + 2 + 3 = 666.

It is not a de Polignac number, because 21351431663523 - 2⁶ = 21351431663459 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21351431663533) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2872528 + ... + 7138226.

It is an arithmetic number, because the mean of its divisors is an integer number (698721660000).

Almost surely, 2^{21351431663523} is an apocalyptic number.

21351431663523 is a deficient number, since it is larger than the sum of its proper divisors (12187208016477).

21351431663523 is a wasteful number, since it uses less digits than its factorization.

21351431663523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4266136 (or 4266133 counting only the distinct ones).

The product of its digits is 1166400, while the sum is 45.

The spelling of 21351431663523 in words is "twenty-one trillion, three hundred fifty-one billion, four hundred thirty-one million, six hundred sixty-three thousand, five hundred twenty-three".