21660563124173 has 2 divisors, whose sum is σ = 21660563124174. Its totient is φ = 21660563124172.

The previous prime is 21660563124127. The next prime is 21660563124191. The reversal of 21660563124173 is 37142136506612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20188289087044 + 1472274037129 = 4493138^2 + 1213373^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21660563124173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21660563120173) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830281562086 + 10830281562087.

It is an arithmetic number, because the mean of its divisors is an integer number (10830281562087).

Almost surely, 2^{21660563124173} is an apocalyptic number.

It is an amenable number.

21660563124173 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660563124173 is an equidigital number, since it uses as much as digits as its factorization.

21660563124173 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1088640, while the sum is 47.

The spelling of 21660563124173 in words is "twenty-one trillion, six hundred sixty billion, five hundred sixty-three million, one hundred twenty-four thousand, one hundred seventy-three".