198217921 has 8 divisors (see below), whose sum is σ = 217137888. Its totient is φ = 179448000.

The previous prime is 198217913. The next prime is 198217931. The reversal of 198217921 is 129712891.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 198217921 - 2³ = 198217913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (198217931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34735 + ... + 40036.

It is an arithmetic number, because the mean of its divisors is an integer number (27142236).

Almost surely, 2^198217921 is an apocalyptic number.

198217921 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

198217921 is a deficient number, since it is larger than the sum of its proper divisors (18919967).

198217921 is a wasteful number, since it uses less digits than its factorization.

198217921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75023.

The product of its digits is 18144, while the sum is 40.

The square root of 198217921 is about 14078.9886355519. The cubic root of 198217921 is about 583.0614194653.

The spelling of 198217921 in words is "one hundred ninety-eight million, two hundred seventeen thousand, nine hundred twenty-one".