643761040 has 80 divisors (see below), whose sum is σ = 1696766400. Its totient is φ = 225179136.

The previous prime is 643761037. The next prime is 643761043. The reversal of 643761040 is 40167346.

It is an interprime number because it is at equal distance from previous prime (643761037) and next prime (643761043).

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 643760993 and 643761011.

It is not an unprimeable number, because it can be changed into a prime (643761043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3471 + ... + 36049.

It is an arithmetic number, because the mean of its divisors is an integer number (21209580).

Almost surely, 2^643761040 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 643761040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (848383200).

643761040 is an abundant number, since it is smaller than the sum of its proper divisors (1053005360).

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

643761040 is a wasteful number, since it uses less digits than its factorization.

643761040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32624 (or 32618 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 31.

The square root of 643761040 is about 25372.4464725024. The cubic root of 643761040 is about 863.4586872768.

The spelling of 643761040 in words is "six hundred forty-three million, seven hundred sixty-one thousand, forty".