645905 has 16 divisors (see below), whose sum is σ = 880320. Its totient is φ = 451008.

The previous prime is 645901. The next prime is 645907. The reversal of 645905 is 509546.

645905 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 645905 - 2² = 645901 is a prime.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645905.

It is not an unprimeable number, because it can be changed into a prime (645901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 974 + ... + 1496.

It is an arithmetic number, because the mean of its divisors is an integer number (55020).

2⁶⁴⁵⁹⁰⁵ is an apocalyptic number.

645905 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

645905 is a deficient number, since it is larger than the sum of its proper divisors (234415).

645905 is a wasteful number, since it uses less digits than its factorization.

645905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 560.

The product of its (nonzero) digits is 5400, while the sum is 29.

The square root of 645905 is about 803.6821511020. The cubic root of 645905 is about 86.4416169678.

The spelling of 645905 in words is "six hundred forty-five thousand, nine hundred five".