645109 has 4 divisors (see below), whose sum is σ = 646720. Its totient is φ = 643500.

The previous prime is 645097. The next prime is 645131. The reversal of 645109 is 901546.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 645109 - 2⁵ = 645077 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 (645149) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 322 + ... + 1180.

It is an arithmetic number, because the mean of its divisors is an integer number (161680).

2⁶⁴⁵¹⁰⁹ is an apocalyptic number.

It is an amenable number.

645109 is a deficient number, since it is larger than the sum of its proper divisors (1611).

645109 is an equidigital number, since it uses as much as digits as its factorization.

645109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1610.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 645109 is about 803.1867777796. The cubic root of 645109 is about 86.4060927488.

The spelling of 645109 in words is "six hundred forty-five thousand, one hundred nine".