20718987584917 has 2 divisors, whose sum is σ = 20718987584918. Its totient is φ = 20718987584916.

The previous prime is 20718987584899. The next prime is 20718987584989. The reversal of 20718987584917 is 71948578981702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19970253878481 + 748733706436 = 4468809^2 + 865294^2 .

It is a cyclic number.

It is not a de Polignac number, because 20718987584917 - 2³⁵ = 20684627846549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20718987585917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10359493792458 + 10359493792459.

It is an arithmetic number, because the mean of its divisors is an integer number (10359493792459).

Almost surely, 2^{20718987584917} is an apocalyptic number.

It is an amenable number.

20718987584917 is a deficient number, since it is larger than the sum of its proper divisors (1).

20718987584917 is an equidigital number, since it uses as much as digits as its factorization.

20718987584917 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 568995840, while the sum is 76.

The spelling of 20718987584917 in words is "twenty trillion, seven hundred eighteen billion, nine hundred eighty-seven million, five hundred eighty-four thousand, nine hundred seventeen".