21261231261539 has 2 divisors, whose sum is σ = 21261231261540. Its totient is φ = 21261231261538.

The previous prime is 21261231261511. The next prime is 21261231261551. The reversal of 21261231261539 is 93516213216212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21261231261539 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21261231261539.

It is not a weakly prime, because it can be changed into another prime (21261231261239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10630615630769 + 10630615630770.

It is an arithmetic number, because the mean of its divisors is an integer number (10630615630770).

Almost surely, 2^{21261231261539} is an apocalyptic number.

21261231261539 is a deficient number, since it is larger than the sum of its proper divisors (1).

21261231261539 is an equidigital number, since it uses as much as digits as its factorization.

21261231261539 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 233280, while the sum is 44.

The spelling of 21261231261539 in words is "twenty-one trillion, two hundred sixty-one billion, two hundred thirty-one million, two hundred sixty-one thousand, five hundred thirty-nine".