198999990 has 96 divisors (see below), whose sum is σ = 613267200. Its totient is φ = 45481824.

The previous prime is 198999967. The next prime is 199000003. The reversal of 198999990 is 99999891.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 11161 + ... + 22859.

It is an arithmetic number, because the mean of its divisors is an integer number (6388200).

Almost surely, 2^198999990 is an apocalyptic number.

198999990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 198999990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (306633600).

198999990 is an abundant number, since it is smaller than the sum of its proper divisors (414267210).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

198999990 is a wasteful number, since it uses less digits than its factorization.

198999990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11728 (or 11716 counting only the distinct ones).

The product of its (nonzero) digits is 4251528, while the sum is 63.

The square root of 198999990 is about 14106.7356252253. The cubic root of 198999990 is about 583.8272363020.

Subtracting from 198999990 its reverse (99999891), we obtain a palindrome (99000099).

It can be divided in two parts, 19 and 8999990, that added together give a palindrome (9000009).

The spelling of 198999990 in words is "one hundred ninety-eight million, nine hundred ninety-nine thousand, nine hundred ninety".