643538551 has 18 divisors (see below), whose sum is σ = 685445712. Its totient is φ = 604133640.

The previous prime is 643538513. The next prime is 643538603. The reversal of 643538551 is 155835346.

It is not a de Polignac number, because 643538551 - 2⁹ = 643538039 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643538251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 2374546 + ... + 2374816.

Almost surely, 2^643538551 is an apocalyptic number.

643538551 is a deficient number, since it is larger than the sum of its proper divisors (41907161).

643538551 is an equidigital number, since it uses as much as digits as its factorization.

643538551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 451 (or 361 counting only the distinct ones).

The product of its digits is 216000, while the sum is 40.

The square root of 643538551 is about 25368.0616326908. The cubic root of 643538551 is about 863.3592030563.

The spelling of 643538551 in words is "six hundred forty-three million, five hundred thirty-eight thousand, five hundred fifty-one".