668528640 has 520 divisors, whose sum is σ = 2664106368. Its totient is φ = 159252480.

The previous prime is 668528639. The next prime is 668528659. The reversal of 668528640 is 46825866.

668528640 is a `hidden beast` number, since 6 + 68 + 528 + 64 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (520).

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 polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 21565425 + ... + 21565455.

Almost surely, 2^668528640 is an apocalyptic number.

668528640 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 668528640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1332053184).

668528640 is an abundant number, since it is smaller than the sum of its proper divisors (1995577728).

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

668528640 is a wasteful number, since it uses less digits than its factorization.

668528640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85 (or 54 counting only the distinct ones).

The product of its (nonzero) digits is 552960, while the sum is 45.

The square root of 668528640 is about 25855.9207919579. The cubic root of 668528640 is about 874.3930005101.

The spelling of 668528640 in words is "six hundred sixty-eight million, five hundred twenty-eight thousand, six hundred forty".