643806553 has 4 divisors (see below), whose sum is σ = 693330148. Its totient is φ = 594282960.

The previous prime is 643806533. The next prime is 643806571. The reversal of 643806553 is 355608346.

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 92871769 + 550934784 = 9637^2 + 23472^2 .

It is a cyclic number.

It is not a de Polignac number, because 643806553 - 2⁵ = 643806521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643806533) 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, 24761778 + ... + 24761803.

It is an arithmetic number, because the mean of its divisors is an integer number (173332537).

Almost surely, 2^643806553 is an apocalyptic number.

It is an amenable number.

643806553 is a deficient number, since it is larger than the sum of its proper divisors (49523595).

643806553 is a wasteful number, since it uses less digits than its factorization.

643806553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49523594.

The product of its (nonzero) digits is 259200, while the sum is 40.

The square root of 643806553 is about 25373.3433547887. The cubic root of 643806553 is about 863.4790352355.

The spelling of 643806553 in words is "six hundred forty-three million, eight hundred six thousand, five hundred fifty-three".