643509 has 12 divisors (see below), whose sum is σ = 938496. Its totient is φ = 424872.

The previous prime is 643507. The next prime is 643523. The reversal of 643509 is 905346.

It is a happy number.

It is not a de Polignac number, because 643509 - 2¹ = 643507 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643507) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 862 + ... + 1424.

It is an arithmetic number, because the mean of its divisors is an integer number (78208).

2⁶⁴³⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

643509 is a deficient number, since it is larger than the sum of its proper divisors (294987).

643509 is a wasteful number, since it uses less digits than its factorization.

643509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 696 (or 693 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 27.

The square root of 643509 is about 802.1901270896. The cubic root of 643509 is about 86.3345987832.

The spelling of 643509 in words is "six hundred forty-three thousand, five hundred nine".