668638 has 4 divisors (see below), whose sum is σ = 1002960. Its totient is φ = 334318.

The previous prime is 668623. The next prime is 668671. The reversal of 668638 is 836866.

It is a semiprime because it is the product of two primes.

It is a junction number, because it is equal to n+sod(n) for n = 668597 and 668606.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 167158 + ... + 167161.

It is an arithmetic number, because the mean of its divisors is an integer number (250740).

2⁶⁶⁸⁶³⁸ is an apocalyptic number.

668638 is a deficient number, since it is larger than the sum of its proper divisors (334322).

668638 is a wasteful number, since it uses less digits than its factorization.

668638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334321.

The product of its digits is 41472, while the sum is 37.

The square root of 668638 is about 817.7028800243. The cubic root of 668638 is about 87.4440676555. Note that the first 3 decimals are identical.

It can be divided in two parts, 6686 and 38, that added together give a square (6724 = 82²).

The spelling of 668638 in words is "six hundred sixty-eight thousand, six hundred thirty-eight".