668646 has 36 divisors (see below), whose sum is σ = 1597596. Its totient is φ = 201960.

The previous prime is 668623. The next prime is 668671. The reversal of 668646 is 646866.

668646 is a `hidden beast` number, since 6 + 6 + 8 + 646 = 666.

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 668646.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 2025 + ... + 2331.

2⁶⁶⁸⁶⁴⁶ is an apocalyptic number.

668646 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 668646, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (798798).

668646 is an abundant number, since it is smaller than the sum of its proper divisors (928950).

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

668646 is a wasteful number, since it uses less digits than its factorization.

668646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 337 (or 323 counting only the distinct ones).

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

The square root of 668646 is about 817.7077717620. The cubic root of 668646 is about 87.4444163992. Note that the first 4 decimals are identical.

The spelling of 668646 in words is "six hundred sixty-eight thousand, six hundred forty-six".