645724 has 12 divisors (see below), whose sum is σ = 1160824. Its totient is φ = 314064.

The previous prime is 645713. The next prime is 645727. The reversal of 645724 is 427546.

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 junction number, because it is equal to n+sod(n) for n = 645692 and 645701.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645727) 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 3 ways as a sum of consecutive naturals, for example, 2034 + ... + 2329.

2⁶⁴⁵⁷²⁴ is an apocalyptic number.

It is an amenable number.

645724 is a deficient number, since it is larger than the sum of its proper divisors (515100).

645724 is a wasteful number, since it uses less digits than its factorization.

645724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4404 (or 4402 counting only the distinct ones).

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

The square root of 645724 is about 803.5695365057. The cubic root of 645724 is about 86.4335417894.

It can be divided in two parts, 645 and 724, that added together give a square (1369 = 37²).

The spelling of 645724 in words is "six hundred forty-five thousand, seven hundred twenty-four".