666988 has 36 divisors (see below), whose sum is σ = 1407672. Its totient is φ = 275520.

The previous prime is 666983. The next prime is 666989. The reversal of 666988 is 889666.

666988 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (666983) 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, 7995 + ... + 8077.

It is an arithmetic number, because the mean of its divisors is an integer number (39102).

2⁶⁶⁶⁹⁸⁸ 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 666988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (703836).

666988 is an abundant number, since it is smaller than the sum of its proper divisors (740684).

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

666988 is a wasteful number, since it uses less digits than its factorization.

666988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142 (or 133 counting only the distinct ones).

The product of its digits is 124416, while the sum is 43.

The square root of 666988 is about 816.6933328980. The cubic root of 666988 is about 87.3720797453.

The spelling of 666988 in words is "six hundred sixty-six thousand, nine hundred eighty-eight".