21198221 has 4 divisors (see below), whose sum is σ = 23125344. Its totient is φ = 19271100.

The previous prime is 21198187. The next prime is 21198223. The reversal of 21198221 is 12289112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21198221 - 2¹⁴ = 21181837 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21198223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 963545 + ... + 963566.

It is an arithmetic number, because the mean of its divisors is an integer number (5781336).

Almost surely, 2^21198221 is an apocalyptic number.

It is an amenable number.

21198221 is a deficient number, since it is larger than the sum of its proper divisors (1927123).

21198221 is a wasteful number, since it uses less digits than its factorization.

21198221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1927122.

The product of its digits is 576, while the sum is 26.

The square root of 21198221 is about 4604.1525821806. The cubic root of 21198221 is about 276.7577589113.

The spelling of 21198221 in words is "twenty-one million, one hundred ninety-eight thousand, two hundred twenty-one".