21351431663461 has 2 divisors, whose sum is σ = 21351431663462. Its totient is φ = 21351431663460.

The previous prime is 21351431663459. The next prime is 21351431663477. The reversal of 21351431663461 is 16436613415312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12037222080900 + 9314209582561 = 3469470^2 + 3051919^2 .

It is a cyclic number.

It is not a de Polignac number, because 21351431663461 - 2¹ = 21351431663459 is a prime.

Together with 21351431663459, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21351431763461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10675715831730 + 10675715831731.

It is an arithmetic number, because the mean of its divisors is an integer number (10675715831731).

Almost surely, 2^{21351431663461} is an apocalyptic number.

It is an amenable number.

21351431663461 is a deficient number, since it is larger than the sum of its proper divisors (1).

21351431663461 is an equidigital number, since it uses as much as digits as its factorization.

21351431663461 is an evil number, because the sum of its binary digits is even.

The product of its digits is 933120, while the sum is 46.

The spelling of 21351431663461 in words is "twenty-one trillion, three hundred fifty-one billion, four hundred thirty-one million, six hundred sixty-three thousand, four hundred sixty-one".