21312540251 has 2 divisors, whose sum is σ = 21312540252. Its totient is φ = 21312540250.

The previous prime is 21312540203. The next prime is 21312540287. The reversal of 21312540251 is 15204521312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21312540251 - 2⁶ = 21312540187 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21312540251.

It is not a weakly prime, because it can be changed into another prime (21312540751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656270125 + 10656270126.

It is an arithmetic number, because the mean of its divisors is an integer number (10656270126).

Almost surely, 2^21312540251 is an apocalyptic number.

21312540251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312540251 is an equidigital number, since it uses as much as digits as its factorization.

21312540251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2400, while the sum is 26.

The spelling of 21312540251 in words is "twenty-one billion, three hundred twelve million, five hundred forty thousand, two hundred fifty-one".