665385840 has 200 divisors, whose sum is σ = 2641304160. Its totient is φ = 152077824.

The previous prime is 665385823. The next prime is 665385859. The reversal of 665385840 is 48583566.

665385840 is a `hidden beast` number, since 6 + 65 + 3 + 8 + 584 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

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, 38026 + ... + 52694.

Almost surely, 2^665385840 is an apocalyptic number.

665385840 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 665385840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1320652080).

665385840 is an abundant number, since it is smaller than the sum of its proper divisors (1975918320).

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

665385840 is a wasteful number, since it uses less digits than its factorization.

665385840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14701 (or 14686 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 45.

The square root of 665385840 is about 25795.0739483336. The cubic root of 665385840 is about 873.0206534951.

The spelling of 665385840 in words is "six hundred sixty-five million, three hundred eighty-five thousand, eight hundred forty".