666987 has 4 divisors (see below), whose sum is σ = 889320. Its totient is φ = 444656.

The previous prime is 666983. The next prime is 666989. The reversal of 666987 is 789666.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 666987 - 2² = 666983 is a prime.

It is a D-number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 666987.

It is not an unprimeable number, because it can be changed into a prime (666983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111162 + ... + 111167.

It is an arithmetic number, because the mean of its divisors is an integer number (222330).

2⁶⁶⁶⁹⁸⁷ is an apocalyptic number.

666987 is a deficient number, since it is larger than the sum of its proper divisors (222333).

666987 is a wasteful number, since it uses less digits than its factorization.

666987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222332.

The product of its digits is 108864, while the sum is 42.

The square root of 666987 is about 816.6927206728. The cubic root of 666987 is about 87.3720360803.

It can be divided in two parts, 666 and 987, that added together give a triangular number (1653 = T₅₇).

The spelling of 666987 in words is "six hundred sixty-six thousand, nine hundred eighty-seven".