643541637 has 4 divisors (see below), whose sum is σ = 858055520. Its totient is φ = 429027756.

The previous prime is 643541623. The next prime is 643541641. The reversal of 643541637 is 736145346.

643541637 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-643541637 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643541595 and 643541604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643542637) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107256937 + ... + 107256942.

It is an arithmetic number, because the mean of its divisors is an integer number (214513880).

Almost surely, 2^643541637 is an apocalyptic number.

It is an amenable number.

643541637 is a deficient number, since it is larger than the sum of its proper divisors (214513883).

643541637 is a wasteful number, since it uses less digits than its factorization.

643541637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214513882.

The product of its digits is 181440, while the sum is 39.

The square root of 643541637 is about 25368.1224571311. The cubic root of 643541637 is about 863.3605830940.

The spelling of 643541637 in words is "six hundred forty-three million, five hundred forty-one thousand, six hundred thirty-seven".