664987 has 4 divisors (see below), whose sum is σ = 669600. Its totient is φ = 660376.

The previous prime is 664973. The next prime is 664997. The reversal of 664987 is 789466.

664987 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 789466 = 2 ⋅394733.

It is a cyclic number.

It is not a de Polignac number, because 664987 - 2¹¹ = 662939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664967) 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, 2083 + ... + 2380.

It is an arithmetic number, because the mean of its divisors is an integer number (167400).

2⁶⁶⁴⁹⁸⁷ is an apocalyptic number.

664987 is a deficient number, since it is larger than the sum of its proper divisors (4613).

664987 is a wasteful number, since it uses less digits than its factorization.

664987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4612.

The product of its digits is 72576, while the sum is 40.

The square root of 664987 is about 815.4673506646. The cubic root of 664987 is about 87.2846185725.

The spelling of 664987 in words is "six hundred sixty-four thousand, nine hundred eighty-seven".