21373999 has 8 divisors (see below), whose sum is σ = 21986640. Its totient is φ = 20769216.

The previous prime is 21373991. The next prime is 21374011. The reversal of 21373999 is 99937312.

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

It is not a de Polignac number, because 21373999 - 2³ = 21373991 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 (21373991) 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, 3787 + ... + 7555.

It is an arithmetic number, because the mean of its divisors is an integer number (2748330).

Almost surely, 2^21373999 is an apocalyptic number.

21373999 is a deficient number, since it is larger than the sum of its proper divisors (612641).

21373999 is a wasteful number, since it uses less digits than its factorization.

21373999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3929.

The product of its digits is 91854, while the sum is 43.

The square root of 21373999 is about 4623.2022451976. The cubic root of 21373999 is about 277.5206228755.

The spelling of 21373999 in words is "twenty-one million, three hundred seventy-three thousand, nine hundred ninety-nine".