643531633 has 2 divisors, whose sum is σ = 643531634. Its totient is φ = 643531632.

The previous prime is 643531631. The next prime is 643531667. The reversal of 643531633 is 336135346.

643531633 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (643531667) can be obtained adding 643531633 to its sum of digits (34).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 495374049 + 148157584 = 22257^2 + 12172^2 .

It is a cyclic number.

It is not a de Polignac number, because 643531633 - 2¹ = 643531631 is a prime.

Together with 643531631, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (643531631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321765816 + 321765817.

It is an arithmetic number, because the mean of its divisors is an integer number (321765817).

Almost surely, 2^643531633 is an apocalyptic number.

It is an amenable number.

643531633 is a deficient number, since it is larger than the sum of its proper divisors (1).

643531633 is an equidigital number, since it uses as much as digits as its factorization.

643531633 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 58320, while the sum is 34.

The square root of 643531633 is about 25367.9252797701. The cubic root of 643531633 is about 863.3561093591.

Adding to 643531633 its reverse (336135346), we get a palindrome (979666979).

The spelling of 643531633 in words is "six hundred forty-three million, five hundred thirty-one thousand, six hundred thirty-three".