1566216171581 has 2 divisors, whose sum is σ = 1566216171582. Its totient is φ = 1566216171580.

The previous prime is 1566216171511. The next prime is 1566216171617. The reversal of 1566216171581 is 1851716126651.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1197512187481 + 368703984100 = 1094309^2 + 607210^2 .

It is a cyclic number.

It is not a de Polignac number, because 1566216171581 - 2¹⁰ = 1566216170557 is a prime.

It is a super-2 number, since 2×1566216171581² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1566216171511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 783108085790 + 783108085791.

It is an arithmetic number, because the mean of its divisors is an integer number (783108085791).

Almost surely, 2^{1566216171581} is an apocalyptic number.

It is an amenable number.

1566216171581 is a deficient number, since it is larger than the sum of its proper divisors (1).

1566216171581 is an equidigital number, since it uses as much as digits as its factorization.

1566216171581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 604800, while the sum is 50.

The spelling of 1566216171581 in words is "one trillion, five hundred sixty-six billion, two hundred sixteen million, one hundred seventy-one thousand, five hundred eighty-one".