20555509 has 4 divisors (see below), whose sum is σ = 22136716. Its totient is φ = 18974304.

The previous prime is 20555503. The next prime is 20555527. The reversal of 20555509 is 90555502.

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 12404484 + 8151025 = 3522^2 + 2855^2 .

It is a cyclic number.

It is not a de Polignac number, because 20555509 - 2³ = 20555501 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20555501) 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, 790584 + ... + 790609.

It is an arithmetic number, because the mean of its divisors is an integer number (5534179).

Almost surely, 2^20555509 is an apocalyptic number.

It is an amenable number.

20555509 is a deficient number, since it is larger than the sum of its proper divisors (1581207).

20555509 is a wasteful number, since it uses less digits than its factorization.

20555509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1581206.

The product of its (nonzero) digits is 11250, while the sum is 31.

The square root of 20555509 is about 4533.8183686601. The cubic root of 20555509 is about 273.9319853559.

The spelling of 20555509 in words is "twenty million, five hundred fifty-five thousand, five hundred nine".