645639 has 16 divisors (see below), whose sum is σ = 929280. Its totient is φ = 397440.

The previous prime is 645629. The next prime is 645641. The reversal of 645639 is 936546.

It is a happy number.

645639 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 645639 - 2⁸ = 645383 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645629) 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, 2559 + ... + 2799.

It is an arithmetic number, because the mean of its divisors is an integer number (58080).

2⁶⁴⁵⁶³⁹ is an apocalyptic number.

645639 is a deficient number, since it is larger than the sum of its proper divisors (283641).

645639 is a wasteful number, since it uses less digits than its factorization.

645639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310.

The product of its digits is 19440, while the sum is 33.

The square root of 645639 is about 803.5166457517. The cubic root of 645639 is about 86.4297490578.

The spelling of 645639 in words is "six hundred forty-five thousand, six hundred thirty-nine".