645688 has 16 divisors (see below), whose sum is σ = 1239480. Its totient is φ = 315168.

The previous prime is 645683. The next prime is 645691. The reversal of 645688 is 886546.

645688 = T₇₇ + T₇₈ + ... + T₁₆₂.

645688 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645683) 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, 595 + ... + 1282.

2⁶⁴⁵⁶⁸⁸ is an apocalyptic number.

It is an amenable number.

645688 is a deficient number, since it is larger than the sum of its proper divisors (593792).

645688 is a wasteful number, since it uses less digits than its factorization.

645688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1926 (or 1922 counting only the distinct ones).

The product of its digits is 46080, while the sum is 37.

The square root of 645688 is about 803.5471361407. The cubic root of 645688 is about 86.4319354967.

The spelling of 645688 in words is "six hundred forty-five thousand, six hundred eighty-eight".