21955921903117 has 2 divisors, whose sum is σ = 21955921903118. Its totient is φ = 21955921903116.

The previous prime is 21955921903039. The next prime is 21955921903147. The reversal of 21955921903117 is 71130912955912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14111547693156 + 7844374209961 = 3756534^2 + 2800781^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21955921903117 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21955921903147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10977960951558 + 10977960951559.

It is an arithmetic number, because the mean of its divisors is an integer number (10977960951559).

Almost surely, 2^{21955921903117} is an apocalyptic number.

It is an amenable number.

21955921903117 is a deficient number, since it is larger than the sum of its proper divisors (1).

21955921903117 is an equidigital number, since it uses as much as digits as its factorization.

21955921903117 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1530900, while the sum is 55.

The spelling of 21955921903117 in words is "twenty-one trillion, nine hundred fifty-five billion, nine hundred twenty-one million, nine hundred three thousand, one hundred seventeen".