17998861 has 2 divisors, whose sum is σ = 17998862. Its totient is φ = 17998860.

The previous prime is 17998859. The next prime is 17998873. The reversal of 17998861 is 16889971.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17388900 + 609961 = 4170^2 + 781^2 .

It is a cyclic number.

It is not a de Polignac number, because 17998861 - 2¹ = 17998859 is a prime.

Together with 17998859, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (17998831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8999430 + 8999431.

It is an arithmetic number, because the mean of its divisors is an integer number (8999431).

Almost surely, 2^17998861 is an apocalyptic number.

It is an amenable number.

17998861 is a deficient number, since it is larger than the sum of its proper divisors (1).

17998861 is an equidigital number, since it uses as much as digits as its factorization.

17998861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 217728, while the sum is 49.

The square root of 17998861 is about 4242.5064525584. The cubic root of 17998861 is about 262.0686114812.

The spelling of 17998861 in words is "seventeen million, nine hundred ninety-eight thousand, eight hundred sixty-one".