668981 has 4 divisors (see below), whose sum is σ = 670752. Its totient is φ = 667212.

The previous prime is 668963. The next prime is 668989. The reversal of 668981 is 189866.

668981 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, and also an emirpimes, since its reverse is a distinct semiprime: 189866 = 2 ⋅94933.

It is a cyclic number.

It is not a de Polignac number, because 668981 - 2¹⁸ = 406837 is a prime.

It is a super-2 number, since 2×668981² = 895071156722, which contains 22 as substring.

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 668981.

It is not an unprimeable number, because it can be changed into a prime (668989) 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, 65 + ... + 1158.

It is an arithmetic number, because the mean of its divisors is an integer number (167688).

2⁶⁶⁸⁹⁸¹ is an apocalyptic number.

It is an amenable number.

668981 is a deficient number, since it is larger than the sum of its proper divisors (1771).

668981 is a wasteful number, since it uses less digits than its factorization.

668981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1770.

The product of its digits is 20736, while the sum is 38.

The square root of 668981 is about 817.9125870165. The cubic root of 668981 is about 87.4590175427.

The spelling of 668981 in words is "six hundred sixty-eight thousand, nine hundred eighty-one".