21244399 has 4 divisors (see below), whose sum is σ = 23175720. Its totient is φ = 19313080.

The previous prime is 21244369. The next prime is 21244417. The reversal of 21244399 is 99344212.

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 21244399 - 2⁵ = 21244367 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 (21244309) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 965644 + ... + 965665.

It is an arithmetic number, because the mean of its divisors is an integer number (5793930).

Almost surely, 2^21244399 is an apocalyptic number.

21244399 is a deficient number, since it is larger than the sum of its proper divisors (1931321).

21244399 is a wasteful number, since it uses less digits than its factorization.

21244399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1931320.

The product of its digits is 15552, while the sum is 34.

The square root of 21244399 is about 4609.1646748625. The cubic root of 21244399 is about 276.9585753065.

The spelling of 21244399 in words is "twenty-one million, two hundred forty-four thousand, three hundred ninety-nine".