20911217 has 4 divisors (see below), whose sum is σ = 20978340. Its totient is φ = 20844096.

The previous prime is 20911213. The next prime is 20911223. The reversal of 20911217 is 71211902.

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 516961 + 20394256 = 719^2 + 4516^2 .

It is a cyclic number.

It is not a de Polignac number, because 20911217 - 2² = 20911213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20911192 and 20911201.

It is not an unprimeable number, because it can be changed into a prime (20911211) by changing a digit.

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

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33092 + ... + 33717.

It is an arithmetic number, because the mean of its divisors is an integer number (5244585).

Almost surely, 2^20911217 is an apocalyptic number.

It is an amenable number.

20911217 is a deficient number, since it is larger than the sum of its proper divisors (67123).

20911217 is an equidigital number, since it uses as much as digits as its factorization.

20911217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67122.

The product of its (nonzero) digits is 252, while the sum is 23.

The square root of 20911217 is about 4572.8784151779. The cubic root of 20911217 is about 275.5030659417.

The spelling of 20911217 in words is "twenty million, nine hundred eleven thousand, two hundred seventeen".