645540 has 96 divisors (see below), whose sum is σ = 2177280. Its totient is φ = 139776.

The previous prime is 645529. The next prime is 645571. The reversal of 645540 is 45546.

645540 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 645540.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645540.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12154 + ... + 12206.

It is an arithmetic number, because the mean of its divisors is an integer number (22680).

2⁶⁴⁵⁵⁴⁰ is an apocalyptic number.

645540 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1088640).

645540 is an abundant number, since it is smaller than the sum of its proper divisors (1531740).

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

645540 is a wasteful number, since it uses less digits than its factorization.

645540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101 (or 99 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 24.

The square root of 645540 is about 803.4550391901. The cubic root of 645540 is about 86.4253312214.

The spelling of 645540 in words is "six hundred forty-five thousand, five hundred forty".