645660 has 72 divisors (see below), whose sum is σ = 2083536. Its totient is φ = 161280.

The previous prime is 645649. The next prime is 645661. The reversal of 645660 is 66546.

645660 is nontrivially palindromic in base 11.

645660 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645661) by changing a digit.

645660 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2955 + ... + 3165.

It is an arithmetic number, because the mean of its divisors is an integer number (28938).

2⁶⁴⁵⁶⁶⁰ is an apocalyptic number.

645660 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 645660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1041768).

645660 is an abundant number, since it is smaller than the sum of its proper divisors (1437876).

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

645660 is a wasteful number, since it uses less digits than its factorization.

645660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243 (or 238 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 645660 is about 803.5297132029. The cubic root of 645660 is about 86.4306861166.

The spelling of 645660 in words is "six hundred forty-five thousand, six hundred sixty".