643521323 has 2 divisors, whose sum is σ = 643521324. Its totient is φ = 643521322.

The previous prime is 643521311. The next prime is 643521331. The reversal of 643521323 is 323125346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643521323 - 2⁶ = 643521259 is a prime.

It is a super-4 number, since 4×643521323⁴ (a number of 36 digits) contains 4444 as substring.

It is equal to p_33474035 and since 643521323 and 33474035 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (643521023) 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, 321760661 + 321760662.

It is an arithmetic number, because the mean of its divisors is an integer number (321760662).

Almost surely, 2^643521323 is an apocalyptic number.

643521323 is a deficient number, since it is larger than the sum of its proper divisors (1).

643521323 is an equidigital number, since it uses as much as digits as its factorization.

643521323 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960, while the sum is 29.

The square root of 643521323 is about 25367.7220695907. The cubic root of 643521323 is about 863.3514987341.

Adding to 643521323 its reverse (323125346), we get a palindrome (966646669).

The spelling of 643521323 in words is "six hundred forty-three million, five hundred twenty-one thousand, three hundred twenty-three".