640725 has 12 divisors (see below), whose sum is σ = 1059456. Its totient is φ = 341680.

The previous prime is 640691. The next prime is 640727. The reversal of 640725 is 527046.

It is a happy number.

It is not a de Polignac number, because 640725 - 2¹⁰ = 639701 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 640695 and 640704.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4197 + ... + 4346.

It is an arithmetic number, because the mean of its divisors is an integer number (88288).

2⁶⁴⁰⁷²⁵ is an apocalyptic number.

It is an amenable number.

640725 is a deficient number, since it is larger than the sum of its proper divisors (418731).

640725 is a wasteful number, since it uses less digits than its factorization.

640725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8556 (or 8551 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 640725 is about 800.4529967462. The cubic root of 640725 is about 86.2099162620.

The spelling of 640725 in words is "six hundred forty thousand, seven hundred twenty-five".