666778875251 has 4 divisors (see below), whose sum is σ = 666780509904. Its totient is φ = 666777240600.

The previous prime is 666778875229. The next prime is 666778875281. The reversal of 666778875251 is 152578877666.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 666778875251 - 2¹⁰ = 666778874227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666778875281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 355781 + ... + 1208361.

It is an arithmetic number, because the mean of its divisors is an integer number (166695127476).

Almost surely, 2^666778875251 is an apocalyptic number.

666778875251 is a deficient number, since it is larger than the sum of its proper divisors (1634653).

666778875251 is an equidigital number, since it uses as much as digits as its factorization.

666778875251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1634652.

The product of its digits is 237081600, while the sum is 68.

The spelling of 666778875251 in words is "six hundred sixty-six billion, seven hundred seventy-eight million, eight hundred seventy-five thousand, two hundred fifty-one".