20511217 has 2 divisors, whose sum is σ = 20511218. Its totient is φ = 20511216.

The previous prime is 20511157. The next prime is 20511221. The reversal of 20511217 is 71211502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10751841 + 9759376 = 3279^2 + 3124^2 .

It is a cyclic number.

It is not a de Polignac number, because 20511217 - 2¹⁹ = 19986929 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20511194 and 20511203.

It is not a weakly prime, because it can be changed into another prime (20511017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10255608 + 10255609.

It is an arithmetic number, because the mean of its divisors is an integer number (10255609).

Almost surely, 2^20511217 is an apocalyptic number.

It is an amenable number.

20511217 is a deficient number, since it is larger than the sum of its proper divisors (1).

20511217 is an equidigital number, since it uses as much as digits as its factorization.

20511217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 20511217 is about 4528.9311100965. The cubic root of 20511217 is about 273.7350921456.

Adding to 20511217 its reverse (71211502), we get a palindrome (91722719).

The spelling of 20511217 in words is "twenty million, five hundred eleven thousand, two hundred seventeen".