646668 has 72 divisors (see below), whose sum is σ = 1886976. Its totient is φ = 184800.

The previous prime is 646643. The next prime is 646669. The reversal of 646668 is 866646.

646668 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nialpdrome in base 7.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646669) by changing a digit.

646668 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 23 ways as a sum of consecutive naturals, for example, 9073 + ... + 9143.

It is an arithmetic number, because the mean of its divisors is an integer number (26208).

2⁶⁴⁶⁶⁶⁸ 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 646668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (943488).

646668 is an abundant number, since it is smaller than the sum of its proper divisors (1240308).

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

646668 is a wasteful number, since it uses less digits than its factorization.

646668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115 (or 110 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 646668 is about 804.1567011472. The cubic root of 646668 is about 86.4756410633.

The spelling of 646668 in words is "six hundred forty-six thousand, six hundred sixty-eight".