21011223217 has 2 divisors, whose sum is σ = 21011223218. Its totient is φ = 21011223216.

The previous prime is 21011223209. The next prime is 21011223271. The reversal of 21011223217 is 71232211012.

Together with next prime (21011223271) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17307770481 + 3703452736 = 131559^2 + 60856^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011223217 - 2³ = 21011223209 is a prime.

It is not a weakly prime, because it can be changed into another prime (21011223817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505611608 + 10505611609.

It is an arithmetic number, because the mean of its divisors is an integer number (10505611609).

Almost surely, 2^21011223217 is an apocalyptic number.

It is an amenable number.

21011223217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011223217 is an equidigital number, since it uses as much as digits as its factorization.

21011223217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 336, while the sum is 22.

Adding to 21011223217 its reverse (71232211012), we get a palindrome (92243434229).

The spelling of 21011223217 in words is "twenty-one billion, eleven million, two hundred twenty-three thousand, two hundred seventeen".