21712221217 has 2 divisors, whose sum is σ = 21712221218. Its totient is φ = 21712221216.

The previous prime is 21712221199. The next prime is 21712221221. The reversal of 21712221217 is 71212221712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20300265441 + 1411955776 = 142479^2 + 37576^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21712221217 is a prime.

It is a super-2 number, since 2×21712221217² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21712221287) 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 as a sum of consecutive naturals, namely, 10856110608 + 10856110609.

It is an arithmetic number, because the mean of its divisors is an integer number (10856110609).

Almost surely, 2^21712221217 is an apocalyptic number.

It is an amenable number.

21712221217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21712221217 is an equidigital number, since it uses as much as digits as its factorization.

21712221217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1568, while the sum is 28.

Adding to 21712221217 its reverse (71212221712), we get a palindrome (92924442929).

The spelling of 21712221217 in words is "twenty-one billion, seven hundred twelve million, two hundred twenty-one thousand, two hundred seventeen".