21044440217 has 2 divisors, whose sum is σ = 21044440218. Its totient is φ = 21044440216.

The previous prime is 21044440213. The next prime is 21044440253. The reversal of 21044440217 is 71204444012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20665787536 + 378652681 = 143756^2 + 19459^2 .

It is a cyclic number.

It is not a de Polignac number, because 21044440217 - 2² = 21044440213 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21044440217.

It is not a weakly prime, because it can be changed into another prime (21044440211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10522220108 + 10522220109.

It is an arithmetic number, because the mean of its divisors is an integer number (10522220109).

Almost surely, 2^21044440217 is an apocalyptic number.

It is an amenable number.

21044440217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21044440217 is an equidigital number, since it uses as much as digits as its factorization.

21044440217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7168, while the sum is 29.

Adding to 21044440217 its reverse (71204444012), we get a palindrome (92248884229).

The spelling of 21044440217 in words is "twenty-one billion, forty-four million, four hundred forty thousand, two hundred seventeen".