667981 has 4 divisors (see below), whose sum is σ = 707292. Its totient is φ = 628672.

The previous prime is 667963. The next prime is 667987. The reversal of 667981 is 189766.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 586756 + 81225 = 766^2 + 285^2 .

It is a cyclic number.

It is not a de Polignac number, because 667981 - 2⁵ = 667949 is a prime.

It is a super-2 number, since 2×667981² = 892397232722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 667981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (667987) 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, 19630 + ... + 19663.

It is an arithmetic number, because the mean of its divisors is an integer number (176823).

2⁶⁶⁷⁹⁸¹ is an apocalyptic number.

It is an amenable number.

667981 is a deficient number, since it is larger than the sum of its proper divisors (39311).

667981 is a wasteful number, since it uses less digits than its factorization.

667981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39310.

The product of its digits is 18144, while the sum is 37.

The square root of 667981 is about 817.3010461268. The cubic root of 667981 is about 87.4154175840.

The spelling of 667981 in words is "six hundred sixty-seven thousand, nine hundred eighty-one".