645975 has 60 divisors (see below), whose sum is σ = 1350360. Its totient is φ = 302400.

The previous prime is 645973. The next prime is 645979. The reversal of 645975 is 579546.

645975 is a `hidden beast` number, since 64 + 597 + 5 = 666.

It is not a de Polignac number, because 645975 - 2¹ = 645973 is a prime.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 22261 + ... + 22289.

It is an arithmetic number, because the mean of its divisors is an integer number (22506).

2⁶⁴⁵⁹⁷⁵ is an apocalyptic number.

645975 is an abundant number, since it is smaller than the sum of its proper divisors (704385).

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

645975 is a wasteful number, since it uses less digits than its factorization.

645975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62 (or 48 counting only the distinct ones).

The product of its digits is 37800, while the sum is 36.

The square root of 645975 is about 803.7256994771. The cubic root of 645975 is about 86.4447395605. Note that the first 3 decimals are identical.

The spelling of 645975 in words is "six hundred forty-five thousand, nine hundred seventy-five".