21105665573 has 2 divisors, whose sum is σ = 21105665574. Its totient is φ = 21105665572.

The previous prime is 21105665527. The next prime is 21105665599. The reversal of 21105665573 is 37556650112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12615333124 + 8490332449 = 112318^2 + 92143^2 .

It is a cyclic number.

It is not a de Polignac number, because 21105665573 - 2⁶ = 21105665509 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21105665573.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21105665773) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552832786 + 10552832787.

It is an arithmetic number, because the mean of its divisors is an integer number (10552832787).

Almost surely, 2^21105665573 is an apocalyptic number.

It is an amenable number.

21105665573 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105665573 is an equidigital number, since it uses as much as digits as its factorization.

21105665573 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 189000, while the sum is 41.

The spelling of 21105665573 in words is "twenty-one billion, one hundred five million, six hundred sixty-five thousand, five hundred seventy-three".