21198566 has 8 divisors (see below), whose sum is σ = 33471480. Its totient is φ = 10041408.

The previous prime is 21198559. The next prime is 21198631. The reversal of 21198566 is 66589112.

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

It is a Harshad number since it is a multiple of its sum of digits (38), and also a Moran number because the ratio is a prime number: 557857 = 21198566 / (2 + 1 + 1 + 9 + 8 + 5 + 6 + 6).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 278891 + ... + 278966.

It is an arithmetic number, because the mean of its divisors is an integer number (4183935).

Almost surely, 2^21198566 is an apocalyptic number.

21198566 is a deficient number, since it is larger than the sum of its proper divisors (12272914).

21198566 is a wasteful number, since it uses less digits than its factorization.

21198566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 557878.

The product of its digits is 25920, while the sum is 38.

The square root of 21198566 is about 4604.1900482061. The cubic root of 21198566 is about 276.7592603094.

Multiplying 21198566 by its sum of digits (38), we get a palindrome (805545508).

The spelling of 21198566 in words is "twenty-one million, one hundred ninety-eight thousand, five hundred sixty-six".