646656 has 40 divisors (see below), whose sum is σ = 1726824. Its totient is φ = 215040.

The previous prime is 646643. The next prime is 646669. The reversal of 646656 is 656646.

646656 = T₂₅₉ + T₂₆₀ + ... + T₂₇₆.

It is an interprime number because it is at equal distance from previous prime (646643) and next prime (646669).

It is a super-4 number, since 4×646656⁴ (a number of 24 digits) contains 4444 as substring.

It is a congruent number.

It is an unprimeable number.

646656 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 3 ways as a sum of consecutive naturals, for example, 1326 + ... + 1746.

646656 is a Friedman number, since it can be written as 6^6+6*(6+4)^5, using all its digits and the basic arithmetic operations.

2⁶⁴⁶⁶⁵⁶ 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 646656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (863412).

646656 is an abundant number, since it is smaller than the sum of its proper divisors (1080168).

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

646656 is an equidigital number, since it uses as much as digits as its factorization.

646656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 442 (or 426 counting only the distinct ones).

The product of its digits is 25920, while the sum is 33.

The square root of 646656 is about 804.1492398803. The cubic root of 646656 is about 86.4751061602.

It can be divided in two parts, 6 and 46656, that multiplied together give a 7-th power (279936 = 6⁷).

The spelling of 646656 in words is "six hundred forty-six thousand, six hundred fifty-six".