643469209 has 4 divisors (see below), whose sum is σ = 644306740. Its totient is φ = 642631680.

The previous prime is 643469207. The next prime is 643469221. The reversal of 643469209 is 902964346.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 902964346 = 2 ⋅451482173.

It can be written as a sum of positive squares in 2 ways, for example, as 161798400 + 481670809 = 12720^2 + 21947^2 .

It is a cyclic number.

It is not a de Polignac number, because 643469209 - 2¹ = 643469207 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643469207) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 417612 + ... + 419149.

It is an arithmetic number, because the mean of its divisors is an integer number (161076685).

Almost surely, 2^643469209 is an apocalyptic number.

It is an amenable number.

643469209 is a deficient number, since it is larger than the sum of its proper divisors (837531).

643469209 is an equidigital number, since it uses as much as digits as its factorization.

643469209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 837530.

The product of its (nonzero) digits is 279936, while the sum is 43.

The square root of 643469209 is about 25366.6948773387. The cubic root of 643469209 is about 863.3281926353.

The spelling of 643469209 in words is "six hundred forty-three million, four hundred sixty-nine thousand, two hundred nine".