643980 has 24 divisors (see below), whose sum is σ = 1803312. Its totient is φ = 171712.

The previous prime is 643969. The next prime is 643991. The reversal of 643980 is 89346.

643980 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 (643969) and next prime (643991).

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

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643980.

It is an unprimeable number.

643980 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 7 ways as a sum of consecutive naturals, for example, 5307 + ... + 5426.

It is an arithmetic number, because the mean of its divisors is an integer number (75138).

2⁶⁴³⁹⁸⁰ is an apocalyptic number.

643980 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

643980 is an abundant number, since it is smaller than the sum of its proper divisors (1159332).

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

643980 is a wasteful number, since it uses less digits than its factorization.

643980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10745 (or 10743 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 643980 is about 802.4836446931. The cubic root of 643980 is about 86.3556571156.

The spelling of 643980 in words is "six hundred forty-three thousand, nine hundred eighty".