669986 has 4 divisors (see below), whose sum is σ = 1004982. Its totient is φ = 334992.

The previous prime is 669971. The next prime is 669989. The reversal of 669986 is 689966.

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

It can be written as a sum of positive squares in only one way, i.e., 609961 + 60025 = 781^2 + 245^2 .

It is a d-powerful number, because it can be written as 6² + 6² + 9⁵ + 9⁶ + 8⁵ + 6⁶ .

It is a Curzon number.

It is a congruent number.

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 as a sum of consecutive naturals, namely, 167495 + ... + 167498.

2⁶⁶⁹⁹⁸⁶ is an apocalyptic number.

669986 is a deficient number, since it is larger than the sum of its proper divisors (334996).

669986 is a wasteful number, since it uses less digits than its factorization.

669986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334995.

The product of its digits is 139968, while the sum is 44.

The square root of 669986 is about 818.5267252815. The cubic root of 669986 is about 87.5027917477.

The spelling of 669986 in words is "six hundred sixty-nine thousand, nine hundred eighty-six".