643892640 has 48 divisors (see below), whose sum is σ = 2028263328. Its totient is φ = 171704576.

The previous prime is 643892633. The next prime is 643892651. The reversal of 643892640 is 46298346.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (48).

It is a junction number, because it is equal to n+sod(n) for n = 643892592 and 643892601.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 670242 + ... + 671201.

It is an arithmetic number, because the mean of its divisors is an integer number (42255486).

Almost surely, 2^643892640 is an apocalyptic number.

643892640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

643892640 is an abundant number, since it is smaller than the sum of its proper divisors (1384370688).

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

643892640 is a wasteful number, since it uses less digits than its factorization.

643892640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1341461 (or 1341453 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 42.

The square root of 643892640 is about 25375.0397044024. The cubic root of 643892640 is about 863.5175204018.

The spelling of 643892640 in words is "six hundred forty-three million, eight hundred ninety-two thousand, six hundred forty".