668551 has 4 divisors (see below), whose sum is σ = 719992. Its totient is φ = 617112.

The previous prime is 668543. The next prime is 668567. The reversal of 668551 is 155866.

668551 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 an emirpimes, since its reverse is a distinct semiprime: 155866 = 2 ⋅77933.

It is a cyclic number.

It is not a de Polignac number, because 668551 - 2³ = 668543 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668531) 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, 25701 + ... + 25726.

It is an arithmetic number, because the mean of its divisors is an integer number (179998).

2⁶⁶⁸⁵⁵¹ is an apocalyptic number.

668551 is a deficient number, since it is larger than the sum of its proper divisors (51441).

668551 is a wasteful number, since it uses less digits than its factorization.

668551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51440.

The product of its digits is 7200, while the sum is 31.

The square root of 668551 is about 817.6496804867. The cubic root of 668551 is about 87.4402748888.

The spelling of 668551 in words is "six hundred sixty-eight thousand, five hundred fifty-one".