656640 has 144 divisors (see below), whose sum is σ = 2452800. Its totient is φ = 165888.

The previous prime is 656609. The next prime is 656651. The reversal of 656640 is 46656.

656640 is a `hidden beast` number, since 656 + 6 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 4.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 656640.

It is an unprimeable number.

656640 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 15 ways as a sum of consecutive naturals, for example, 34551 + ... + 34569.

2⁶⁵⁶⁶⁴⁰ is an apocalyptic number.

656640 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 656640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1226400).

656640 is an abundant number, since it is smaller than the sum of its proper divisors (1796160).

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

656640 is a wasteful number, since it uses less digits than its factorization.

656640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49 (or 29 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 656640 is about 810.3332647744. Note that the first 3 decimals coincide. The cubic root of 656640 is about 86.9178773213.

It can be divided in two parts, 656 and 640, that added together give a 4-th power (1296 = 6⁴).

The spelling of 656640 in words is "six hundred fifty-six thousand, six hundred forty".