20505217 has 2 divisors, whose sum is σ = 20505218. Its totient is φ = 20505216.

The previous prime is 20505209. The next prime is 20505227. The reversal of 20505217 is 71250502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15492096 + 5013121 = 3936^2 + 2239^2 .

It is a cyclic number.

It is not a de Polignac number, because 20505217 - 2³ = 20505209 is a prime.

It is not a weakly prime, because it can be changed into another prime (20505227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10252608 + 10252609.

It is an arithmetic number, because the mean of its divisors is an integer number (10252609).

Almost surely, 2^20505217 is an apocalyptic number.

It is an amenable number.

20505217 is a deficient number, since it is larger than the sum of its proper divisors (1).

20505217 is an equidigital number, since it uses as much as digits as its factorization.

20505217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 20505217 is about 4528.2686536909. The cubic root of 20505217 is about 273.7083982846.

Adding to 20505217 its reverse (71250502), we get a palindrome (91755719).

The spelling of 20505217 in words is "twenty million, five hundred five thousand, two hundred seventeen".