643343440 has 40 divisors (see below), whose sum is σ = 1502348040. Its totient is φ = 256206336.

The previous prime is 643343429. The next prime is 643343471. The reversal of 643343440 is 44343346.

It can be written as a sum of positive squares in 4 ways, for example, as 25522704 + 617820736 = 5052^2 + 24856^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 762 + ... + 35878.

It is an arithmetic number, because the mean of its divisors is an integer number (37558701).

Almost surely, 2^643343440 is an apocalyptic number.

It is an amenable number.

643343440 is an abundant number, since it is smaller than the sum of its proper divisors (859004600).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643343440 is a wasteful number, since it uses less digits than its factorization.

643343440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35359 (or 35353 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 31.

The square root of 643343440 is about 25364.2157379250. The cubic root of 643343440 is about 863.2719418223.

Adding to 643343440 its reverse (44343346), we get a palindrome (687686786).

The spelling of 643343440 in words is "six hundred forty-three million, three hundred forty-three thousand, four hundred forty".