643800040 has 64 divisors (see below), whose sum is σ = 1598078160. Its totient is φ = 231905280.

The previous prime is 643800023. The next prime is 643800043. The reversal of 643800040 is 40008346.

It can be written as a sum of positive squares in 8 ways, for example, as 8054244 + 635745796 = 2838^2 + 25214^2 .

It is a junction number, because it is equal to n+sod(n) for n = 643799978 and 643800014.

It is not an unprimeable number, because it can be changed into a prime (643800043) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6222 + ... + 36418.

Almost surely, 2^643800040 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 643800040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (799039080).

643800040 is an abundant number, since it is smaller than the sum of its proper divisors (954278120).

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

643800040 is a wasteful number, since it uses less digits than its factorization.

643800040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30262 (or 30258 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 25.

The square root of 643800040 is about 25373.2150111096. The cubic root of 643800040 is about 863.4761234613.

Adding to 643800040 its reverse (40008346), we get a palindrome (683808386).

The spelling of 643800040 in words is "six hundred forty-three million, eight hundred thousand, forty".