645780 has 48 divisors (see below), whose sum is σ = 1854720. Its totient is φ = 167808.

The previous prime is 645763. The next prime is 645787. The reversal of 645780 is 87546.

It is a happy number.

645780 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645787) by changing a digit.

645780 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 15 ways as a sum of consecutive naturals, for example, 2706 + ... + 2934.

It is an arithmetic number, because the mean of its divisors is an integer number (38640).

2⁶⁴⁵⁷⁸⁰ is an apocalyptic number.

645780 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 645780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (927360).

645780 is an abundant number, since it is smaller than the sum of its proper divisors (1208940).

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

645780 is a wasteful number, since it uses less digits than its factorization.

645780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288 (or 286 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 645780 is about 803.6043802768. The cubic root of 645780 is about 86.4360403484.

The spelling of 645780 in words is "six hundred forty-five thousand, seven hundred eighty".