643221632 has 32 divisors (see below), whose sum is σ = 1283005980. Its totient is φ = 321212416.

The previous prime is 643221617. The next prime is 643221661. The reversal of 643221632 is 236122346.

It can be written as a sum of positive squares in 2 ways, for example, as 641912896 + 1308736 = 25336^2 + 1144^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is a junction number, because it is equal to n+sod(n) for n = 643221595 and 643221604.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 119348 + ... + 124620.

Almost surely, 2^643221632 is an apocalyptic number.

It is an amenable number.

643221632 is a deficient number, since it is larger than the sum of its proper divisors (639784348).

643221632 is an equidigital number, since it uses as much as digits as its factorization.

643221632 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6240 (or 6228 counting only the distinct ones).

The product of its digits is 10368, while the sum is 29.

The square root of 643221632 is about 25361.8144461314. The cubic root of 643221632 is about 863.2174555976.

Adding to 643221632 its reverse (236122346), we get a palindrome (879343978).

The spelling of 643221632 in words is "six hundred forty-three million, two hundred twenty-one thousand, six hundred thirty-two".