643553321 has 8 divisors (see below), whose sum is σ = 661277064. Its totient is φ = 625847040.

The previous prime is 643553311. The next prime is 643553333. The reversal of 643553321 is 123355346.

643553321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 1488400 + 642064921 = 1220^2 + 25339^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 643553321 - 2¹⁴ = 643536937 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643553311) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 112691 + ... + 118263.

It is an arithmetic number, because the mean of its divisors is an integer number (82659633).

Almost surely, 2^643553321 is an apocalyptic number.

It is an amenable number.

643553321 is a deficient number, since it is larger than the sum of its proper divisors (17723743).

643553321 is a wasteful number, since it uses less digits than its factorization.

643553321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8731.

The product of its digits is 32400, while the sum is 32.

The square root of 643553321 is about 25368.3527451035. The cubic root of 643553321 is about 863.3658080571.

It can be divided in two parts, 64355 and 3321, that added together give a palindrome (67676).

The spelling of 643553321 in words is "six hundred forty-three million, five hundred fifty-three thousand, three hundred twenty-one".