21112207805917 has 2 divisors, whose sum is σ = 21112207805918. Its totient is φ = 21112207805916.

The previous prime is 21112207805903. The next prime is 21112207805921. The reversal of 21112207805917 is 71950870221112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17714578259161 + 3397629546756 = 4208869^2 + 1843266^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21112207805917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21112807805917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556103902958 + 10556103902959.

It is an arithmetic number, because the mean of its divisors is an integer number (10556103902959).

Almost surely, 2^{21112207805917} is an apocalyptic number.

It is an amenable number.

21112207805917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112207805917 is an equidigital number, since it uses as much as digits as its factorization.

21112207805917 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 141120, while the sum is 46.

The spelling of 21112207805917 in words is "twenty-one trillion, one hundred twelve billion, two hundred seven million, eight hundred five thousand, nine hundred seventeen".