668621 has 8 divisors (see below), whose sum is σ = 692664. Its totient is φ = 645120.

The previous prime is 668617. The next prime is 668623. The reversal of 668621 is 126866.

It can be written as a sum of positive squares in 4 ways, for example, as 44521 + 624100 = 211^2 + 790^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 668621 - 2² = 668617 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 668621.

It is not an unprimeable number, because it can be changed into a prime (668623) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 5861 + ... + 5973.

It is an arithmetic number, because the mean of its divisors is an integer number (86583).

2⁶⁶⁸⁶²¹ is an apocalyptic number.

668621 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

668621 is a deficient number, since it is larger than the sum of its proper divisors (24043).

668621 is a wasteful number, since it uses less digits than its factorization.

668621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271.

The product of its digits is 3456, while the sum is 29.

The square root of 668621 is about 817.6924849844. The cubic root of 668621 is about 87.4433265661.

The spelling of 668621 in words is "six hundred sixty-eight thousand, six hundred twenty-one".