643771638 has 48 divisors (see below), whose sum is σ = 1496411280. Its totient is φ = 207186336.

The previous prime is 643771603. The next prime is 643771649. The reversal of 643771638 is 836177346.

643771638 is a `hidden beast` number, since 6 + 4 + 3 + 7 + 7 + 1 + 638 = 666.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 643771593 and 643771602.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8745 + ... + 36932.

It is an arithmetic number, because the mean of its divisors is an integer number (31175235).

Almost surely, 2^643771638 is an apocalyptic number.

643771638 is an abundant number, since it is smaller than the sum of its proper divisors (852639642).

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

643771638 is a wasteful number, since it uses less digits than its factorization.

643771638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45723 (or 45711 counting only the distinct ones).

The product of its digits is 508032, while the sum is 45.

The square root of 643771638 is about 25372.6553202458. The cubic root of 643771638 is about 863.4634255179.

The spelling of 643771638 in words is "six hundred forty-three million, seven hundred seventy-one thousand, six hundred thirty-eight".