21431715251 has 2 divisors, whose sum is σ = 21431715252. Its totient is φ = 21431715250.

The previous prime is 21431715241. The next prime is 21431715257. The reversal of 21431715251 is 15251713412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21431715251 - 2⁶ = 21431715187 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21431715257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715857625 + 10715857626.

It is an arithmetic number, because the mean of its divisors is an integer number (10715857626).

Almost surely, 2^21431715251 is an apocalyptic number.

21431715251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21431715251 is an equidigital number, since it uses as much as digits as its factorization.

21431715251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8400, while the sum is 32.

The spelling of 21431715251 in words is "twenty-one billion, four hundred thirty-one million, seven hundred fifteen thousand, two hundred fifty-one".