21205144 has 32 divisors (see below), whose sum is σ = 41450400. Its totient is φ = 10160640.

The previous prime is 21205139. The next prime is 21205157. The reversal of 21205144 is 44150212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20512 + ... + 21520.

It is an arithmetic number, because the mean of its divisors is an integer number (1295325).

Almost surely, 2^21205144 is an apocalyptic number.

It is an amenable number.

21205144 is a deficient number, since it is larger than the sum of its proper divisors (20245256).

21205144 is a wasteful number, since it uses less digits than its factorization.

21205144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1123 (or 1119 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 21205144 is about 4604.9043421118. The cubic root of 21205144 is about 276.7878838516.

Adding to 21205144 its reverse (44150212), we get a palindrome (65355356).

The spelling of 21205144 in words is "twenty-one million, two hundred five thousand, one hundred forty-four".