666791817768 has 48 divisors (see below), whose sum is σ = 1912123598580. Its totient is φ = 209189589504.

The previous prime is 666791817733. The next prime is 666791817793. The reversal of 666791817768 is 867718197666.

It can be written as a sum of positive squares in 2 ways, for example, as 641725962084 + 25065855684 = 801078^2 + 158322^2 .

It is a super-2 number, since 2×666791817768² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a junction number, because it is equal to n+sod(n) for n = 666791817696 and 666791817705.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 272381055 + ... + 272383502.

Almost surely, 2^666791817768 is an apocalyptic number.

666791817768 is a gapful number since it is divisible by the number (68) formed by its first and last digit.

It is an amenable number.

666791817768 is an abundant number, since it is smaller than the sum of its proper divisors (1245331780812).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666791817768 is a wasteful number, since it uses less digits than its factorization.

666791817768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 544764586 (or 544764579 counting only the distinct ones).

The product of its digits is 256048128, while the sum is 72.

The spelling of 666791817768 in words is "six hundred sixty-six billion, seven hundred ninety-one million, eight hundred seventeen thousand, seven hundred sixty-eight".