643955620 has 96 divisors (see below), whose sum is σ = 1693310976. Its totient is φ = 199843200.

The previous prime is 643955593. The next prime is 643955621. The reversal of 643955620 is 26559346.

It is not an unprimeable number, because it can be changed into a prime (643955621) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 416569 + ... + 418111.

It is an arithmetic number, because the mean of its divisors is an integer number (17638656).

Almost surely, 2^643955620 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 643955620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (846655488).

643955620 is an abundant number, since it is smaller than the sum of its proper divisors (1049355356).

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

643955620 is a wasteful number, since it uses less digits than its factorization.

643955620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1841 (or 1839 counting only the distinct ones).

The product of its (nonzero) digits is 194400, while the sum is 40.

The square root of 643955620 is about 25376.2806573383. The cubic root of 643955620 is about 863.5456734183.

The spelling of 643955620 in words is "six hundred forty-three million, nine hundred fifty-five thousand, six hundred twenty".