21956126917 has 2 divisors, whose sum is σ = 21956126918. Its totient is φ = 21956126916.

The previous prime is 21956126897. The next prime is 21956126921. The reversal of 21956126917 is 71962165912.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21809087041 + 147039876 = 147679^2 + 12126^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21956126917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21956126947) 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, 10978063458 + 10978063459.

It is an arithmetic number, because the mean of its divisors is an integer number (10978063459).

Almost surely, 2^21956126917 is an apocalyptic number.

It is an amenable number.

21956126917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21956126917 is an equidigital number, since it uses as much as digits as its factorization.

21956126917 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 408240, while the sum is 49.

The spelling of 21956126917 in words is "twenty-one billion, nine hundred fifty-six million, one hundred twenty-six thousand, nine hundred seventeen".