643720 has 96 divisors (see below), whose sum is σ = 1915200. Its totient is φ = 190080.

The previous prime is 643703. The next prime is 643723. The reversal of 643720 is 27346.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a junction number, because it is equal to n+sod(n) for n = 643691 and 643700.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643723) by changing a digit.

643720 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, 33871 + ... + 33889.

It is an arithmetic number, because the mean of its divisors is an integer number (19950).

2⁶⁴³⁷²⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (957600).

643720 is an abundant number, since it is smaller than the sum of its proper divisors (1271480).

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

643720 is a wasteful number, since it uses less digits than its factorization.

It is an anagram of its base 12 representation: 643720 = (270634)₁₂.

643720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59 (or 44 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 22.

The square root of 643720 is about 802.3216312677. The cubic root of 643720 is about 86.3440338285.

The spelling of 643720 in words is "six hundred forty-three thousand, seven hundred twenty".