645989 has 8 divisors (see below), whose sum is σ = 672672. Its totient is φ = 619920.

The previous prime is 645979. The next prime is 646003. The reversal of 645989 is 989546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 645989 - 2⁴ = 645973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645979) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3479 + ... + 3659.

It is an arithmetic number, because the mean of its divisors is an integer number (84084).

2⁶⁴⁵⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

645989 is a deficient number, since it is larger than the sum of its proper divisors (26683).

645989 is a wasteful number, since it uses less digits than its factorization.

645989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 307.

The product of its digits is 77760, while the sum is 41.

The square root of 645989 is about 803.7344088690. The cubic root of 645989 is about 86.4453640519.

The spelling of 645989 in words is "six hundred forty-five thousand, nine hundred eighty-nine".