664720 has 40 divisors (see below), whose sum is σ = 1767744. Its totient is φ = 227712.

The previous prime is 664711. The next prime is 664739. The reversal of 664720 is 27466.

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

It is an unprimeable number.

664720 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34 + ... + 1153.

2⁶⁶⁴⁷²⁰ 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 664720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (883872).

664720 is an abundant number, since it is smaller than the sum of its proper divisors (1103024).

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

664720 is a wasteful number, since it uses less digits than its factorization.

664720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1207 (or 1201 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 25.

The square root of 664720 is about 815.3036244247. The cubic root of 664720 is about 87.2729350795.

The spelling of 664720 in words is "six hundred sixty-four thousand, seven hundred twenty".