666640044 has 120 divisors (see below), whose sum is σ = 1999380768. Its totient is φ = 189734400.

The previous prime is 666640043. The next prime is 666640069. The reversal of 666640044 is 440046666.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 666639990 and 666640008.

It is not an unprimeable number, because it can be changed into a prime (666640043) 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 39 ways as a sum of consecutive naturals, for example, 909102 + ... + 909834.

Almost surely, 2^666640044 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 666640044, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (999690384).

666640044 is an abundant number, since it is smaller than the sum of its proper divisors (1332740724).

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

666640044 is a wasteful number, since it uses less digits than its factorization.

666640044 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1157 (or 1146 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 36.

The square root of 666640044 is about 25819.3734238459. The cubic root of 666640044 is about 873.5688360607.

The spelling of 666640044 in words is "six hundred sixty-six million, six hundred forty thousand, forty-four".