666778728 has 96 divisors (see below), whose sum is σ = 2094079680. Its totient is φ = 173184000.

The previous prime is 666778727. The next prime is 666778781. The reversal of 666778728 is 827877666.

It is a super-2 number, since 2×666778728² = 889187744226595968, which contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (666778727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3928 + ... + 36728.

It is an arithmetic number, because the mean of its divisors is an integer number (21813330).

Almost surely, 2^666778728 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 666778728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1047039840).

666778728 is an abundant number, since it is smaller than the sum of its proper divisors (1427300952).

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

666778728 is a wasteful number, since it uses less digits than its factorization.

666778728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32839 (or 32824 counting only the distinct ones).

The product of its digits is 9483264, while the sum is 57.

The square root of 666778728 is about 25822.0589419202. The cubic root of 666778728 is about 873.6294092898.

The spelling of 666778728 in words is "six hundred sixty-six million, seven hundred seventy-eight thousand, seven hundred twenty-eight".