19998166 has 4 divisors (see below), whose sum is σ = 29997252. Its totient is φ = 9999082.

The previous prime is 19998163. The next prime is 19998169. The reversal of 19998166 is 66189991.

19998166 is nontrivially palindromic in base 15.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (19998163) and next prime (19998169).

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19998161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4999540 + ... + 4999543.

It is an arithmetic number, because the mean of its divisors is an integer number (7499313).

Almost surely, 2^19998166 is an apocalyptic number.

19998166 is a deficient number, since it is larger than the sum of its proper divisors (9999086).

19998166 is an equidigital number, since it uses as much as digits as its factorization.

19998166 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9999085.

The product of its digits is 209952, while the sum is 49.

The square root of 19998166 is about 4471.9309028651. The cubic root of 19998166 is about 271.4334643360.

It can be divided in two parts, 19998 and 166, that added together give a square (20164 = 142²).

The spelling of 19998166 in words is "nineteen million, nine hundred ninety-eight thousand, one hundred sixty-six".