645984 has 36 divisors (see below), whose sum is σ = 1837836. Its totient is φ = 215232.

The previous prime is 645979. The next prime is 646003. The reversal of 645984 is 489546.

645984 is a `hidden beast` number, since 64 + 598 + 4 = 666.

645984 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645984.

It is an unprimeable number.

645984 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 834 + ... + 1409.

It is an arithmetic number, because the mean of its divisors is an integer number (51051).

2⁶⁴⁵⁹⁸⁴ is an apocalyptic number.

It is an amenable number.

645984 is an abundant number, since it is smaller than the sum of its proper divisors (1191852).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645984 is a wasteful number, since it uses less digits than its factorization.

645984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2259 (or 2248 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The square root of 645984 is about 803.7312983827. The cubic root of 645984 is about 86.4451410203.

The spelling of 645984 in words is "six hundred forty-five thousand, nine hundred eighty-four".