21231117217 has 2 divisors, whose sum is σ = 21231117218. Its totient is φ = 21231117216.

The previous prime is 21231117197. The next prime is 21231117221. The reversal of 21231117217 is 71271113212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16547220496 + 4683896721 = 128636^2 + 68439^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21231117217 is a prime.

It is not a weakly prime, because it can be changed into another prime (21231117247) 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, 10615558608 + 10615558609.

It is an arithmetic number, because the mean of its divisors is an integer number (10615558609).

Almost surely, 2^21231117217 is an apocalyptic number.

It is an amenable number.

21231117217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231117217 is an equidigital number, since it uses as much as digits as its factorization.

21231117217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1176, while the sum is 28.

The spelling of 21231117217 in words is "twenty-one billion, two hundred thirty-one million, one hundred seventeen thousand, two hundred seventeen".