21172222517 has 2 divisors, whose sum is σ = 21172222518. Its totient is φ = 21172222516.

The previous prime is 21172222483. The next prime is 21172222523. The reversal of 21172222517 is 71522227112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20843851876 + 328370641 = 144374^2 + 18121^2 .

It is a cyclic number.

It is not a de Polignac number, because 21172222517 - 2⁸ = 21172222261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21172222537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10586111258 + 10586111259.

It is an arithmetic number, because the mean of its divisors is an integer number (10586111259).

Almost surely, 2^21172222517 is an apocalyptic number.

It is an amenable number.

21172222517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21172222517 is an equidigital number, since it uses as much as digits as its factorization.

21172222517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7840, while the sum is 32.

Adding to 21172222517 its reverse (71522227112), we get a palindrome (92694449629).

The spelling of 21172222517 in words is "twenty-one billion, one hundred seventy-two million, two hundred twenty-two thousand, five hundred seventeen".