20540209 has 2 divisors, whose sum is σ = 20540210. Its totient is φ = 20540208.

The previous prime is 20540171. The next prime is 20540227. The reversal of 20540209 is 90204502.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17640000 + 2900209 = 4200^2 + 1703^2 .

It is a cyclic number.

It is not a de Polignac number, because 20540209 - 2¹⁹ = 20015921 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20540209.

It is not a weakly prime, because it can be changed into another prime (20540239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10270104 + 10270105.

It is an arithmetic number, because the mean of its divisors is an integer number (10270105).

Almost surely, 2^20540209 is an apocalyptic number.

It is an amenable number.

20540209 is a deficient number, since it is larger than the sum of its proper divisors (1).

20540209 is an equidigital number, since it uses as much as digits as its factorization.

20540209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 20540209 is about 4532.1307350958. The cubic root of 20540209 is about 273.8640035857.

The spelling of 20540209 in words is "twenty million, five hundred forty thousand, two hundred nine".