668557 has 4 divisors (see below), whose sum is σ = 671296. Its totient is φ = 665820.

The previous prime is 668543. The next prime is 668567. The reversal of 668557 is 755866.

668557 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 963 + ... + 1504.

It is an arithmetic number, because the mean of its divisors is an integer number (167824).

2⁶⁶⁸⁵⁵⁷ is an apocalyptic number.

It is an amenable number.

668557 is a deficient number, since it is larger than the sum of its proper divisors (2739).

668557 is a wasteful number, since it uses less digits than its factorization.

668557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2738.

The product of its digits is 50400, while the sum is 37.

The square root of 668557 is about 817.6533495315. The cubic root of 668557 is about 87.4405364695.

It can be divided in two parts, 668 and 557, that added together give a triangular number (1225 = T₄₉).

The spelling of 668557 in words is "six hundred sixty-eight thousand, five hundred fifty-seven".