643521337 has 4 divisors (see below), whose sum is σ = 643908580. Its totient is φ = 643134096.

The previous prime is 643521331. The next prime is 643521371. The reversal of 643521337 is 733125346.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 257634601 + 385886736 = 16051^2 + 19644^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643521337 is a prime.

It is a super-2 number, since 2×643521337² = 828239422348535138, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643521331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 191118 + ... + 194455.

It is an arithmetic number, because the mean of its divisors is an integer number (160977145).

Almost surely, 2^643521337 is an apocalyptic number.

It is an amenable number.

643521337 is a deficient number, since it is larger than the sum of its proper divisors (387243).

643521337 is a wasteful number, since it uses less digits than its factorization.

643521337 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 387242.

The product of its digits is 45360, while the sum is 34.

The square root of 643521337 is about 25367.7223455319. The cubic root of 643521337 is about 863.3515049949.

It can be divided in two parts, 6435 and 21337, that added together give a palindrome (27772).

The spelling of 643521337 in words is "six hundred forty-three million, five hundred twenty-one thousand, three hundred thirty-seven".