21173899 has 8 divisors (see below), whose sum is σ = 21909888. Its totient is φ = 20441280.

The previous prime is 21173849. The next prime is 21173903. The reversal of 21173899 is 99837112.

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 21173899 - 2⁹ = 21173387 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21173849) 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, 24279 + ... + 25135.

It is an arithmetic number, because the mean of its divisors is an integer number (2738736).

Almost surely, 2^21173899 is an apocalyptic number.

21173899 is a deficient number, since it is larger than the sum of its proper divisors (735989).

21173899 is an equidigital number, since it uses as much as digits as its factorization.

21173899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1685.

The product of its digits is 27216, while the sum is 40.

The square root of 21173899 is about 4601.5105128642. The cubic root of 21173899 is about 276.6518714367.

The spelling of 21173899 in words is "twenty-one million, one hundred seventy-three thousand, eight hundred ninety-nine".