644725 has 24 divisors (see below), whose sum is σ = 890568. Its totient is φ = 460800.

The previous prime is 644717. The next prime is 644729. The reversal of 644725 is 527446.

It can be written as a sum of positive squares in 12 ways, for example, as 117649 + 527076 = 343^2 + 726^2 .

It is not a de Polignac number, because 644725 - 2³ = 644717 is a prime.

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

Its product of digits (6720) is a multiple of the sum of its prime factors (105).

It is a junction number, because it is equal to n+sod(n) for n = 644693 and 644702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644729) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15705 + ... + 15745.

It is an arithmetic number, because the mean of its divisors is an integer number (37107).

2⁶⁴⁴⁷²⁵ is an apocalyptic number.

It is an amenable number.

644725 is a deficient number, since it is larger than the sum of its proper divisors (245843).

644725 is a wasteful number, since it uses less digits than its factorization.

644725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105 (or 100 counting only the distinct ones).

The product of its digits is 6720, while the sum is 28.

The square root of 644725 is about 802.9476944359. The cubic root of 644725 is about 86.3889449876.

It can be divided in two parts, 644 and 725, that added together give a square (1369 = 37²).

The spelling of 644725 in words is "six hundred forty-four thousand, seven hundred twenty-five".