21016217 has 2 divisors, whose sum is σ = 21016218. Its totient is φ = 21016216.

The previous prime is 21016201. The next prime is 21016241. The reversal of 21016217 is 71261012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20757136 + 259081 = 4556^2 + 509^2 .

It is a cyclic number.

It is not a de Polignac number, because 21016217 - 2⁴ = 21016201 is a prime.

It is not a weakly prime, because it can be changed into another prime (21016277) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10508108 + 10508109.

It is an arithmetic number, because the mean of its divisors is an integer number (10508109).

Almost surely, 2^21016217 is an apocalyptic number.

It is an amenable number.

21016217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21016217 is an equidigital number, since it uses as much as digits as its factorization.

21016217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 21016217 is about 4584.3447732473. The cubic root of 21016217 is about 275.9634175767.

Adding to 21016217 its reverse (71261012), we get a palindrome (92277229).

The spelling of 21016217 in words is "twenty-one million, sixteen thousand, two hundred seventeen".