19998865 has 4 divisors (see below), whose sum is σ = 23998644. Its totient is φ = 15999088.

The previous prime is 19998859. The next prime is 19998877. The reversal of 19998865 is 56889991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56889991 = 31 ⋅1835161.

It can be written as a sum of positive squares in 2 ways, for example, as 7160976 + 12837889 = 2676^2 + 3583^2 .

It is a cyclic number.

It is not a de Polignac number, because 19998865 - 2⁹ = 19998353 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1999882 + ... + 1999891.

It is an arithmetic number, because the mean of its divisors is an integer number (5999661).

Almost surely, 2^19998865 is an apocalyptic number.

It is an amenable number.

19998865 is a deficient number, since it is larger than the sum of its proper divisors (3999779).

19998865 is an equidigital number, since it uses as much as digits as its factorization.

19998865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3999778.

The product of its digits is 1399680, while the sum is 55.

The square root of 19998865 is about 4472.0090563415. The cubic root of 19998865 is about 271.4366267890.

The spelling of 19998865 in words is "nineteen million, nine hundred ninety-eight thousand, eight hundred sixty-five".