21542104621 has 2 divisors, whose sum is σ = 21542104622. Its totient is φ = 21542104620.

The previous prime is 21542104561. The next prime is 21542104669. The reversal of 21542104621 is 12640124512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21137088996 + 405015625 = 145386^2 + 20125^2 .

It is a cyclic number.

It is not a de Polignac number, because 21542104621 - 2²⁹ = 21005233709 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21542104621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21542104121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771052310 + 10771052311.

It is an arithmetic number, because the mean of its divisors is an integer number (10771052311).

Almost surely, 2^21542104621 is an apocalyptic number.

It is an amenable number.

21542104621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21542104621 is an equidigital number, since it uses as much as digits as its factorization.

21542104621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3840, while the sum is 28.

The spelling of 21542104621 in words is "twenty-one billion, five hundred forty-two million, one hundred four thousand, six hundred twenty-one".