21198685 has 4 divisors (see below), whose sum is σ = 25438428. Its totient is φ = 16958944.

The previous prime is 21198679. The next prime is 21198701. The reversal of 21198685 is 58689112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 16826404 + 4372281 = 4102^2 + 2091^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21198685 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

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, 2119864 + ... + 2119873.

It is an arithmetic number, because the mean of its divisors is an integer number (6359607).

Almost surely, 2^21198685 is an apocalyptic number.

It is an amenable number.

21198685 is a deficient number, since it is larger than the sum of its proper divisors (4239743).

21198685 is an equidigital number, since it uses as much as digits as its factorization.

21198685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4239742.

The product of its digits is 34560, while the sum is 40.

The square root of 21198685 is about 4604.2029711992. The cubic root of 21198685 is about 276.7597781792.

The spelling of 21198685 in words is "twenty-one million, one hundred ninety-eight thousand, six hundred eighty-five".