16667566781 has 2 divisors, whose sum is σ = 16667566782. Its totient is φ = 16667566780.

The previous prime is 16667566771. The next prime is 16667566843. The reversal of 16667566781 is 18766576661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16151868100 + 515698681 = 127090^2 + 22709^2 .

It is a cyclic number.

It is not a de Polignac number, because 16667566781 - 2²⁶ = 16600457917 is a prime.

It is a super-2 number, since 2×16667566781² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 16667566781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16667566771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8333783390 + 8333783391.

It is an arithmetic number, because the mean of its divisors is an integer number (8333783391).

Almost surely, 2^16667566781 is an apocalyptic number.

It is an amenable number.

16667566781 is a deficient number, since it is larger than the sum of its proper divisors (1).

16667566781 is an equidigital number, since it uses as much as digits as its factorization.

16667566781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15240960, while the sum is 59.

The spelling of 16667566781 in words is "sixteen billion, six hundred sixty-seven million, five hundred sixty-six thousand, seven hundred eighty-one".