643430521 has 4 divisors (see below), whose sum is σ = 643925632. Its totient is φ = 642935412.

The previous prime is 643430461. The next prime is 643430531. The reversal of 643430521 is 125034346.

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 643430521 - 2⁹ = 643430009 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643430521.

It is not an unprimeable number, because it can be changed into a prime (643430531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 245601 + ... + 248206.

It is an arithmetic number, because the mean of its divisors is an integer number (160981408).

Almost surely, 2^643430521 is an apocalyptic number.

It is an amenable number.

643430521 is a deficient number, since it is larger than the sum of its proper divisors (495111).

643430521 is a wasteful number, since it uses less digits than its factorization.

643430521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 495110.

The product of its (nonzero) digits is 8640, while the sum is 28.

The square root of 643430521 is about 25365.9322911656. The cubic root of 643430521 is about 863.3108900148.

Adding to 643430521 its reverse (125034346), we get a palindrome (768464867).

The spelling of 643430521 in words is "six hundred forty-three million, four hundred thirty thousand, five hundred twenty-one".