21000120217 has 2 divisors, whose sum is σ = 21000120218. Its totient is φ = 21000120216.

The previous prime is 21000120187. The next prime is 21000120221. The reversal of 21000120217 is 71202100012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11170587481 + 9829532736 = 105691^2 + 99144^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000120217 - 2¹¹ = 21000118169 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21000120217.

It is not a weakly prime, because it can be changed into another prime (21000120257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500060108 + 10500060109.

It is an arithmetic number, because the mean of its divisors is an integer number (10500060109).

Almost surely, 2^21000120217 is an apocalyptic number.

It is an amenable number.

21000120217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000120217 is an equidigital number, since it uses as much as digits as its factorization.

21000120217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 56, while the sum is 16.

Adding to 21000120217 its reverse (71202100012), we get a palindrome (92202220229).

The spelling of 21000120217 in words is "twenty-one billion, one hundred twenty thousand, two hundred seventeen".