16566531557 has 2 divisors, whose sum is σ = 16566531558. Its totient is φ = 16566531556.

The previous prime is 16566531539. The next prime is 16566531599. The reversal of 16566531557 is 75513566561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14802615556 + 1763916001 = 121666^2 + 41999^2 .

It is a cyclic number.

It is not a de Polignac number, because 16566531557 - 2²⁰ = 16565482981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16566534557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8283265778 + 8283265779.

It is an arithmetic number, because the mean of its divisors is an integer number (8283265779).

Almost surely, 2^16566531557 is an apocalyptic number.

It is an amenable number.

16566531557 is a deficient number, since it is larger than the sum of its proper divisors (1).

16566531557 is an equidigital number, since it uses as much as digits as its factorization.

16566531557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2835000, while the sum is 50.

The spelling of 16566531557 in words is "sixteen billion, five hundred sixty-six million, five hundred thirty-one thousand, five hundred fifty-seven".