21000121217 has 2 divisors, whose sum is σ = 21000121218. Its totient is φ = 21000121216.

The previous prime is 21000121211. The next prime is 21000121223. The reversal of 21000121217 is 71212100012.

It is a balanced prime because it is at equal distance from previous prime (21000121211) and next prime (21000121223).

It can be written as a sum of positive squares in only one way, i.e., 12937697536 + 8062423681 = 113744^2 + 89791^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000121217 is a prime.

It is a super-2 number, since 2×21000121217² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21000121195 and 21000121204.

It is not a weakly prime, because it can be changed into another prime (21000121211) 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, 10500060608 + 10500060609.

It is an arithmetic number, because the mean of its divisors is an integer number (10500060609).

Almost surely, 2^21000121217 is an apocalyptic number.

It is an amenable number.

21000121217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000121217 is an equidigital number, since it uses as much as digits as its factorization.

21000121217 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 17.

Adding to 21000121217 its reverse (71212100012), we get a palindrome (92212221229).

The spelling of 21000121217 in words is "twenty-one billion, one hundred twenty-one thousand, two hundred seventeen".