21118399 has 4 divisors (see below), whose sum is σ = 21323536. Its totient is φ = 20913264.

The previous prime is 21118381. The next prime is 21118411. The reversal of 21118399 is 99381112.

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

It is a cyclic number.

It is not a de Polignac number, because 21118399 - 2¹¹ = 21116351 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21113399) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 102414 + ... + 102619.

It is an arithmetic number, because the mean of its divisors is an integer number (5330884).

Almost surely, 2^21118399 is an apocalyptic number.

21118399 is a deficient number, since it is larger than the sum of its proper divisors (205137).

21118399 is a wasteful number, since it uses less digits than its factorization.

21118399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205136.

The product of its digits is 3888, while the sum is 34.

The square root of 21118399 is about 4595.4759274748. The cubic root of 21118399 is about 276.4099444358.

The spelling of 21118399 in words is "twenty-one million, one hundred eighteen thousand, three hundred ninety-nine".