21351972461 has 2 divisors, whose sum is σ = 21351972462. Its totient is φ = 21351972460.

The previous prime is 21351972407. The next prime is 21351972491. The reversal of 21351972461 is 16427915312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14464632361 + 6887340100 = 120269^2 + 82990^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21351972461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21351972491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10675986230 + 10675986231.

It is an arithmetic number, because the mean of its divisors is an integer number (10675986231).

Almost surely, 2^21351972461 is an apocalyptic number.

It is an amenable number.

21351972461 is a deficient number, since it is larger than the sum of its proper divisors (1).

21351972461 is an equidigital number, since it uses as much as digits as its factorization.

21351972461 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90720, while the sum is 41.

The spelling of 21351972461 in words is "twenty-one billion, three hundred fifty-one million, nine hundred seventy-two thousand, four hundred sixty-one".