643968738 has 64 divisors (see below), whose sum is σ = 1731697920. Its totient is φ = 173166336.

The previous prime is 643968733. The next prime is 643968739. The reversal of 643968738 is 837869346.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (643968733) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 43681 + ... + 56532.

It is an arithmetic number, because the mean of its divisors is an integer number (27057780).

Almost surely, 2^643968738 is an apocalyptic number.

643968738 is an abundant number, since it is smaller than the sum of its proper divisors (1087729182).

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

643968738 is a wasteful number, since it uses less digits than its factorization.

643968738 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100248 (or 100242 counting only the distinct ones).

The product of its digits is 5225472, while the sum is 54.

The square root of 643968738 is about 25376.5391257358. The cubic root of 643968738 is about 863.5515371325.

The spelling of 643968738 in words is "six hundred forty-three million, nine hundred sixty-eight thousand, seven hundred thirty-eight".