643521331 has 2 divisors, whose sum is σ = 643521332. Its totient is φ = 643521330.

The previous prime is 643521323. The next prime is 643521371. The reversal of 643521331 is 133125346.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643521331 - 2³ = 643521323 is a prime.

It is a super-2 number, since 2×643521331² = 828239406904023122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 643521331.

It is not a weakly prime, because it can be changed into another prime (643521311) 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 as a sum of consecutive naturals, namely, 321760665 + 321760666.

It is an arithmetic number, because the mean of its divisors is an integer number (321760666).

Almost surely, 2^643521331 is an apocalyptic number.

643521331 is a deficient number, since it is larger than the sum of its proper divisors (1).

643521331 is an equidigital number, since it uses as much as digits as its factorization.

643521331 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 28.

The square root of 643521331 is about 25367.7222272714. The cubic root of 643521331 is about 863.3515023117.

Adding to 643521331 its reverse (133125346), we get a palindrome (776646677).

The spelling of 643521331 in words is "six hundred forty-three million, five hundred twenty-one thousand, three hundred thirty-one".