21040804562509 has 2 divisors, whose sum is σ = 21040804562510. Its totient is φ = 21040804562508.

The previous prime is 21040804562483. The next prime is 21040804562567. The reversal of 21040804562509 is 90526540804012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18267264056484 + 2773540506025 = 4274022^2 + 1665395^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21040804562509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21040804562009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10520402281254 + 10520402281255.

It is an arithmetic number, because the mean of its divisors is an integer number (10520402281255).

Almost surely, 2^{21040804562509} is an apocalyptic number.

It is an amenable number.

21040804562509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21040804562509 is an equidigital number, since it uses as much as digits as its factorization.

21040804562509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 691200, while the sum is 46.

The spelling of 21040804562509 in words is "twenty-one trillion, forty billion, eight hundred four million, five hundred sixty-two thousand, five hundred nine".