666403920 has 360 divisors, whose sum is σ = 2805586056. Its totient is φ = 140507136.

The previous prime is 666403919. The next prime is 666403937. The reversal of 666403920 is 29304666.

It can be written as a sum of positive squares in 4 ways, for example, as 121088016 + 545315904 = 11004^2 + 23352^2 .

It is a tau number, because it is divible by the number of its divisors (360).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 457914 + ... + 459366.

Almost surely, 2^666403920 is an apocalyptic number.

666403920 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666403920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1402793028).

666403920 is an abundant number, since it is smaller than the sum of its proper divisors (2139182136).

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

666403920 is a wasteful number, since it uses less digits than its factorization.

666403920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1499 (or 1483 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 36.

The square root of 666403920 is about 25814.8004059687. The cubic root of 666403920 is about 873.4656844783.

The spelling of 666403920 in words is "six hundred sixty-six million, four hundred three thousand, nine hundred twenty".