666491328 has 140 divisors (see below), whose sum is σ = 2000783400. Its totient is φ = 219345408.

The previous prime is 666491327. The next prime is 666491359. The reversal of 666491328 is 823194666.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666491327) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 429498 + ... + 431046.

It is an arithmetic number, because the mean of its divisors is an integer number (14291310).

Almost surely, 2^666491328 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 666491328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1000391700).

666491328 is an abundant number, since it is smaller than the sum of its proper divisors (1334292072).

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

666491328 is a wasteful number, since it uses less digits than its factorization.

666491328 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1656 (or 1637 counting only the distinct ones).

The product of its digits is 373248, while the sum is 45.

The square root of 666491328 is about 25816.4933327514. The cubic root of 666491328 is about 873.5038718041.

The spelling of 666491328 in words is "six hundred sixty-six million, four hundred ninety-one thousand, three hundred twenty-eight".