19998989 has 2 divisors, whose sum is σ = 19998990. Its totient is φ = 19998988.

The previous prime is 19998977. The next prime is 19998991. The reversal of 19998989 is 98989991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13912900 + 6086089 = 3730^2 + 2467^2 .

It is a cyclic number.

It is not a de Polignac number, because 19998989 - 2⁸ = 19998733 is a prime.

It is a super-2 number, since 2×19998989² = 799919122044242, which contains 22 as substring.

Together with 19998991, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19998949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9999494 + 9999495.

It is an arithmetic number, because the mean of its divisors is an integer number (9999495).

Almost surely, 2^19998989 is an apocalyptic number.

It is an amenable number.

19998989 is a deficient number, since it is larger than the sum of its proper divisors (1).

19998989 is an equidigital number, since it uses as much as digits as its factorization.

19998989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3779136, while the sum is 62.

The square root of 19998989 is about 4472.0229203348. The cubic root of 19998989 is about 271.4371877887.

The spelling of 19998989 in words is "nineteen million, nine hundred ninety-eight thousand, nine hundred eighty-nine".