640770 has 64 divisors (see below), whose sum is σ = 1741824. Its totient is φ = 149760.

The previous prime is 640741. The next prime is 640771. The reversal of 640770 is 77046.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 640770.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640771) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12064 + ... + 12116.

It is an arithmetic number, because the mean of its divisors is an integer number (27216).

2⁶⁴⁰⁷⁷⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640770, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (870912).

640770 is an abundant number, since it is smaller than the sum of its proper divisors (1101054).

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

640770 is a wasteful number, since it uses less digits than its factorization.

640770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107.

The product of its (nonzero) digits is 1176, while the sum is 24.

The square root of 640770 is about 800.4811053360. The cubic root of 640770 is about 86.2119344734.

The spelling of 640770 in words is "six hundred forty thousand, seven hundred seventy".