640625 has 14 divisors (see below), whose sum is σ = 820302. Its totient is φ = 500000.

The previous prime is 640621. The next prime is 640631. The reversal of 640625 is 526046.

640625 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 7 ways, for example, as 579121 + 61504 = 761^2 + 248^2 .

It is not a de Polignac number, because 640625 - 2² = 640621 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 640625.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640621) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 15605 + ... + 15645.

It is an arithmetic number, because the mean of its divisors is an integer number (58593).

640625 is a Friedman number, since it can be written as (42-6^0)*5^6, using all its digits and the basic arithmetic operations.

2⁶⁴⁰⁶²⁵ is an apocalyptic number.

It is an amenable number.

640625 is a deficient number, since it is larger than the sum of its proper divisors (179677).

640625 is an frugal number, since it uses more digits than its factorization.

640625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71 (or 46 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 640625 is about 800.3905296791. The cubic root of 640625 is about 86.2054310096.

The spelling of 640625 in words is "six hundred forty thousand, six hundred twenty-five".