16666166681 has 2 divisors, whose sum is σ = 16666166682. Its totient is φ = 16666166680.

The previous prime is 16666166633. The next prime is 16666166701. The reversal of 16666166681 is 18666166661.

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., 12787991056 + 3878175625 = 113084^2 + 62275^2 .

It is a cyclic number.

It is not a de Polignac number, because 16666166681 - 2⁶ = 16666166617 is a prime.

It is a super-2 number, since 2×16666166681² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (16666156681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8333083340 + 8333083341.

It is an arithmetic number, because the mean of its divisors is an integer number (8333083341).

Almost surely, 2^16666166681 is an apocalyptic number.

It is an amenable number.

16666166681 is a deficient number, since it is larger than the sum of its proper divisors (1).

16666166681 is an equidigital number, since it uses as much as digits as its factorization.

16666166681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2239488, while the sum is 53.

The spelling of 16666166681 in words is "sixteen billion, six hundred sixty-six million, one hundred sixty-six thousand, six hundred eighty-one".