669981 has 16 divisors (see below), whose sum is σ = 987840. Its totient is φ = 401280.

The previous prime is 669971. The next prime is 669989. The reversal of 669981 is 189966.

669981 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 669981 - 2⁷ = 669853 is a prime.

It is a super-2 number, since 2×669981² = 897749080722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

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 669981.

It is not an unprimeable number, because it can be changed into a prime (669989) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1390 + ... + 1808.

It is an arithmetic number, because the mean of its divisors is an integer number (61740).

2⁶⁶⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

669981 is a deficient number, since it is larger than the sum of its proper divisors (317859).

669981 is a wasteful number, since it uses less digits than its factorization.

669981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 476.

The product of its digits is 23328, while the sum is 39.

The square root of 669981 is about 818.5236710077. The cubic root of 669981 is about 87.5025740739.

The spelling of 669981 in words is "six hundred sixty-nine thousand, nine hundred eighty-one".