21205338 has 96 divisors (see below), whose sum is σ = 55157760. Its totient is φ = 5372640.

The previous prime is 21205313. The next prime is 21205361. The reversal of 21205338 is 83350212.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 255445 + ... + 255527.

It is an arithmetic number, because the mean of its divisors is an integer number (574560).

Almost surely, 2^21205338 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21205338, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27578880).

21205338 is an abundant number, since it is smaller than the sum of its proper divisors (33952422).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21205338 is a wasteful number, since it uses less digits than its factorization.

21205338 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 192 (or 185 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21205338 is about 4604.9254065620. The cubic root of 21205338 is about 276.7887279343.

The spelling of 21205338 in words is "twenty-one million, two hundred five thousand, three hundred thirty-eight".