21731007917 has 2 divisors, whose sum is σ = 21731007918. Its totient is φ = 21731007916.

The previous prime is 21731007839. The next prime is 21731007931. The reversal of 21731007917 is 71970013712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17418984361 + 4312023556 = 131981^2 + 65666^2 .

It is a cyclic number.

It is not a de Polignac number, because 21731007917 - 2¹⁰ = 21731006893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21731007217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865503958 + 10865503959.

It is an arithmetic number, because the mean of its divisors is an integer number (10865503959).

Almost surely, 2^21731007917 is an apocalyptic number.

It is an amenable number.

21731007917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731007917 is an equidigital number, since it uses as much as digits as its factorization.

21731007917 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18522, while the sum is 38.

The spelling of 21731007917 in words is "twenty-one billion, seven hundred thirty-one million, seven thousand, nine hundred seventeen".