643987740 has 48 divisors (see below), whose sum is σ = 1967091840. Its totient is φ = 156118080.

The previous prime is 643987711. The next prime is 643987759. The reversal of 643987740 is 47789346.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 643987740.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 487210 + ... + 488529.

It is an arithmetic number, because the mean of its divisors is an integer number (40981080).

Almost surely, 2^643987740 is an apocalyptic number.

643987740 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

643987740 is an abundant number, since it is smaller than the sum of its proper divisors (1323104100).

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

643987740 is a wasteful number, since it uses less digits than its factorization.

643987740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 975762 (or 975760 counting only the distinct ones).

The product of its (nonzero) digits is 1016064, while the sum is 48.

The square root of 643987740 is about 25376.9135239099. The cubic root of 643987740 is about 863.5600308393.

The spelling of 643987740 in words is "six hundred forty-three million, nine hundred eighty-seven thousand, seven hundred forty".