645745 has 16 divisors (see below), whose sum is σ = 839808. Its totient is φ = 474880.

The previous prime is 645739. The next prime is 645751. The reversal of 645745 is 547546.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (645739) and next prime (645751).

It is not a de Polignac number, because 645745 - 2³ = 645737 is a prime.

It is a Duffinian number.

Its product of digits (16800) is a multiple of the sum of its prime divisors (200).

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 5982 + ... + 6088.

It is an arithmetic number, because the mean of its divisors is an integer number (52488).

2⁶⁴⁵⁷⁴⁵ is an apocalyptic number.

It is an amenable number.

645745 is a deficient number, since it is larger than the sum of its proper divisors (194063).

645745 is a wasteful number, since it uses less digits than its factorization.

645745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200.

The product of its digits is 16800, while the sum is 31.

The square root of 645745 is about 803.5826030969. The cubic root of 645745 is about 86.4344787659.

The spelling of 645745 in words is "six hundred forty-five thousand, seven hundred forty-five".