643221641 has 4 divisors (see below), whose sum is σ = 652822032. Its totient is φ = 633621252.

The previous prime is 643221617. The next prime is 643221661. The reversal of 643221641 is 146122346.

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 cyclic number.

It is not a de Polignac number, because 643221641 - 2⁶ = 643221577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643221661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4800095 + ... + 4800228.

It is an arithmetic number, because the mean of its divisors is an integer number (163205508).

Almost surely, 2^643221641 is an apocalyptic number.

It is an amenable number.

643221641 is a deficient number, since it is larger than the sum of its proper divisors (9600391).

643221641 is an equidigital number, since it uses as much as digits as its factorization.

643221641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9600390.

The product of its digits is 6912, while the sum is 29.

The square root of 643221641 is about 25361.8146235635. The cubic root of 643221641 is about 863.2174596236.

Adding to 643221641 its reverse (146122346), we get a palindrome (789343987).

The spelling of 643221641 in words is "six hundred forty-three million, two hundred twenty-one thousand, six hundred forty-one".