21351431663465 has 24 divisors (see below), whose sum is σ = 27178469204040. Its totient is φ = 16099994582784.

The previous prime is 21351431663461. The next prime is 21351431663477. The reversal of 21351431663465 is 56436613415312.

It can be written as a sum of positive squares in 4 ways, for example, as 8004129330649 + 13347302332816 = 2829157^2 + 3653396^2 .

It is not a de Polignac number, because 21351431663465 - 2² = 21351431663461 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21351431663461) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 29667380 + ... + 30378549.

It is an arithmetic number, because the mean of its divisors is an integer number (1132436216835).

Almost surely, 2^{21351431663465} is an apocalyptic number.

It is an amenable number.

21351431663465 is a deficient number, since it is larger than the sum of its proper divisors (5827037540575).

21351431663465 is a wasteful number, since it uses less digits than its factorization.

21351431663465 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60046169 (or 60046150 counting only the distinct ones).

The product of its digits is 4665600, while the sum is 50.

The spelling of 21351431663465 in words is "twenty-one trillion, three hundred fifty-one billion, four hundred thirty-one million, six hundred sixty-three thousand, four hundred sixty-five".