21641211217 has 2 divisors, whose sum is σ = 21641211218. Its totient is φ = 21641211216.

The previous prime is 21641211181. The next prime is 21641211281. The reversal of 21641211217 is 71211214612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20954299536 + 686911681 = 144756^2 + 26209^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21641211217 is a prime.

It is not a weakly prime, because it can be changed into another prime (21641215217) 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, 10820605608 + 10820605609.

It is an arithmetic number, because the mean of its divisors is an integer number (10820605609).

Almost surely, 2^21641211217 is an apocalyptic number.

It is an amenable number.

21641211217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21641211217 is an equidigital number, since it uses as much as digits as its factorization.

21641211217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1344, while the sum is 28.

Adding to 21641211217 its reverse (71211214612), we get a palindrome (92852425829).

The spelling of 21641211217 in words is "twenty-one billion, six hundred forty-one million, two hundred eleven thousand, two hundred seventeen".