666378881 has 12 divisors (see below), whose sum is σ = 776687472. Its totient is φ = 570067848.

The previous prime is 666378877. The next prime is 666378893. The reversal of 666378881 is 188873666.

It is not a de Polignac number, because 666378881 - 2² = 666378877 is a prime.

It is a super-2 number, since 2×666378881² = 888121626085624322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666378841) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12626 + ... + 38628.

It is an arithmetic number, because the mean of its divisors is an integer number (64723956).

Almost surely, 2^666378881 is an apocalyptic number.

It is an amenable number.

666378881 is a deficient number, since it is larger than the sum of its proper divisors (110308591).

666378881 is a wasteful number, since it uses less digits than its factorization.

666378881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26540 (or 26533 counting only the distinct ones).

The product of its digits is 2322432, while the sum is 53.

The square root of 666378881 is about 25814.3154276847. The cubic root of 666378881 is about 873.4547446761.

The spelling of 666378881 in words is "six hundred sixty-six million, three hundred seventy-eight thousand, eight hundred eighty-one".