668781 has 12 divisors (see below), whose sum is σ = 1017120. Its totient is φ = 422280.

The previous prime is 668761. The next prime is 668791. The reversal of 668781 is 187866.

668781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 668781 - 2¹¹ = 666733 is a prime.

It is a super-2 number, since 2×668781² = 894536051922, which contains 22 as substring.

It is a Curzon 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 668781.

It is not an unprimeable number, because it can be changed into a prime (668741) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1785 + ... + 2126.

It is an arithmetic number, because the mean of its divisors is an integer number (84760).

2⁶⁶⁸⁷⁸¹ is an apocalyptic number.

It is an amenable number.

668781 is a deficient number, since it is larger than the sum of its proper divisors (348339).

668781 is a wasteful number, since it uses less digits than its factorization.

668781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3936 (or 3933 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 668781 is about 817.7903154232. The cubic root of 668781 is about 87.4503010286.

Subtracting from 668781 its product of digits (16128), we obtain a triangular number (652653 = T₁₁₄₂).

It can be divided in two parts, 6 and 68781, that multiplied together give a triangular number (412686 = T₉₀₈).

The spelling of 668781 in words is "six hundred sixty-eight thousand, seven hundred eighty-one".