645720 has 32 divisors (see below), whose sum is σ = 1937520. Its totient is φ = 172160.

The previous prime is 645713. The next prime is 645727. The reversal of 645720 is 27546.

It is a happy number.

645720 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (645713) and next prime (645727).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an Ulam number.

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 polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2571 + ... + 2810.

2⁶⁴⁵⁷²⁰ is an apocalyptic number.

645720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645720 is an abundant number, since it is smaller than the sum of its proper divisors (1291800).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645720 is a wasteful number, since it uses less digits than its factorization.

645720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5395 (or 5391 counting only the distinct ones).

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

The square root of 645720 is about 803.5670476071. The cubic root of 645720 is about 86.4333633154.

The spelling of 645720 in words is "six hundred forty-five thousand, seven hundred twenty".