666891984 has 120 divisors (see below), whose sum is σ = 1906475200. Its totient is φ = 200724480.

The previous prime is 666891949. The next prime is 666891989. The reversal of 666891984 is 489198666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666891989) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1155504 + ... + 1156080.

Almost surely, 2^666891984 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666891984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (953237600).

666891984 is an abundant number, since it is smaller than the sum of its proper divisors (1239583216).

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

666891984 is a wasteful number, since it uses less digits than its factorization.

666891984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 809 (or 792 counting only the distinct ones).

The product of its digits is 4478976, while the sum is 57.

The square root of 666891984 is about 25824.2518575079. The cubic root of 666891984 is about 873.6788700613.

The spelling of 666891984 in words is "six hundred sixty-six million, eight hundred ninety-one thousand, nine hundred eighty-four".