665550378864 has 480 divisors, whose sum is σ = 2268636464640. Its totient is φ = 184963792896.

The previous prime is 665550378859. The next prime is 665550378959. The reversal of 665550378864 is 468873055566.

665550378864 is a `hidden beast` number, since 6 + 6 + 5 + 550 + 3 + 78 + 8 + 6 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 155755032 + ... + 155759304.

It is an arithmetic number, because the mean of its divisors is an integer number (4726325968).

Almost surely, 2^665550378864 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 665550378864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1134318232320).

665550378864 is an abundant number, since it is smaller than the sum of its proper divisors (1603086085776).

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

665550378864 is a wasteful number, since it uses less digits than its factorization.

665550378864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4459 (or 4441 counting only the distinct ones).

The product of its (nonzero) digits is 145152000, while the sum is 63.

The spelling of 665550378864 in words is "six hundred sixty-five billion, five hundred fifty million, three hundred seventy-eight thousand, eight hundred sixty-four".