668720 has 40 divisors (see below), whose sum is σ = 1676976. Its totient is φ = 246528.

The previous prime is 668719. The next prime is 668737. The reversal of 668720 is 27866.

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 719 + ... + 1361.

2⁶⁶⁸⁷²⁰ 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 668720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (838488).

668720 is an abundant number, since it is smaller than the sum of its proper divisors (1008256).

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

668720 is a wasteful number, since it uses less digits than its factorization.

668720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 669 (or 663 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 668720 is about 817.7530189489. The cubic root of 668720 is about 87.4476421460.

The spelling of 668720 in words is "six hundred sixty-eight thousand, seven hundred twenty".