645591 has 4 divisors (see below), whose sum is σ = 860792. Its totient is φ = 430392.

The previous prime is 645583. The next prime is 645599. The reversal of 645591 is 195546.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (645583) and next prime (645599).

It is not a de Polignac number, because 645591 - 2³ = 645583 is a prime.

It is a D-number.

It is a Duffinian number.

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 645591.

It is not an unprimeable number, because it can be changed into a prime (645599) 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 3 ways as a sum of consecutive naturals, for example, 107596 + ... + 107601.

It is an arithmetic number, because the mean of its divisors is an integer number (215198).

2⁶⁴⁵⁵⁹¹ is an apocalyptic number.

645591 is a deficient number, since it is larger than the sum of its proper divisors (215201).

645591 is a wasteful number, since it uses less digits than its factorization.

645591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215200.

The product of its digits is 5400, while the sum is 30.

The square root of 645591 is about 803.4867764936. The cubic root of 645591 is about 86.4276071329.

The spelling of 645591 in words is "six hundred forty-five thousand, five hundred ninety-one".