640956 has 24 divisors (see below), whose sum is σ = 1544704. Its totient is φ = 206640.

The previous prime is 640949. The next prime is 640957. The reversal of 640956 is 659046.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640957) by changing a digit.

640956 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, 490 + ... + 1233.

2⁶⁴⁰⁹⁵⁶ is an apocalyptic number.

It is an amenable number.

640956 is an abundant number, since it is smaller than the sum of its proper divisors (903748).

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

640956 is a wasteful number, since it uses less digits than its factorization.

640956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1761 (or 1759 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 640956 is about 800.5972770376. The cubic root of 640956 is about 86.2202754114.

It can be divided in two parts, 640 and 956, that added together give a triangular number (1596 = T₅₆).

The spelling of 640956 in words is "six hundred forty thousand, nine hundred fifty-six".