643507531 has 2 divisors, whose sum is σ = 643507532. Its totient is φ = 643507530.

The previous prime is 643507507. The next prime is 643507573. The reversal of 643507531 is 135705346.

643507531 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643507531 - 2⁵ = 643507499 is a prime.

It is a super-2 number, since 2×643507531² = 828203884907431922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (643507591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321753765 + 321753766.

It is an arithmetic number, because the mean of its divisors is an integer number (321753766).

Almost surely, 2^643507531 is an apocalyptic number.

643507531 is a deficient number, since it is larger than the sum of its proper divisors (1).

643507531 is an equidigital number, since it uses as much as digits as its factorization.

643507531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 37800, while the sum is 34.

The square root of 643507531 is about 25367.4502266192. The cubic root of 643507531 is about 863.3453308841.

The spelling of 643507531 in words is "six hundred forty-three million, five hundred seven thousand, five hundred thirty-one".