643471709 has 4 divisors (see below), whose sum is σ = 681323004. Its totient is φ = 605620416.

The previous prime is 643471663. The next prime is 643471711. The reversal of 643471709 is 907174346.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 326524900 + 316946809 = 18070^2 + 17803^2 .

It is a cyclic number.

It is not a de Polignac number, because 643471709 - 2¹² = 643467613 is a prime.

It is a super-3 number, since 3×643471709³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643476709) 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, 18925622 + ... + 18925655.

It is an arithmetic number, because the mean of its divisors is an integer number (170330751).

Almost surely, 2^643471709 is an apocalyptic number.

It is an amenable number.

643471709 is a deficient number, since it is larger than the sum of its proper divisors (37851295).

643471709 is a wasteful number, since it uses less digits than its factorization.

643471709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37851294.

The product of its (nonzero) digits is 127008, while the sum is 41.

The square root of 643471709 is about 25366.7441545028. The cubic root of 643471709 is about 863.3293106985.

The spelling of 643471709 in words is "six hundred forty-three million, four hundred seventy-one thousand, seven hundred nine".