21055174561 has 2 divisors, whose sum is σ = 21055174562. Its totient is φ = 21055174560.

The previous prime is 21055174523. The next prime is 21055174573. The reversal of 21055174561 is 16547155012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20759334561 + 295840000 = 144081^2 + 17200^2 .

It is a cyclic number.

It is not a de Polignac number, because 21055174561 - 2⁷ = 21055174433 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21055174561.

It is not a weakly prime, because it can be changed into another prime (21055174661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10527587280 + 10527587281.

It is an arithmetic number, because the mean of its divisors is an integer number (10527587281).

Almost surely, 2^21055174561 is an apocalyptic number.

It is an amenable number.

21055174561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21055174561 is an equidigital number, since it uses as much as digits as its factorization.

21055174561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 42000, while the sum is 37.

The spelling of 21055174561 in words is "twenty-one billion, fifty-five million, one hundred seventy-four thousand, five hundred sixty-one".