21209144 has 16 divisors (see below), whose sum is σ = 43382520. Its totient is φ = 9640480.

The previous prime is 21209141. The next prime is 21209161. The reversal of 21209144 is 44190212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21209141) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 120419 + ... + 120594.

Almost surely, 2^21209144 is an apocalyptic number.

It is an amenable number.

21209144 is an abundant number, since it is smaller than the sum of its proper divisors (22173376).

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

21209144 is a wasteful number, since it uses less digits than its factorization.

21209144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241030 (or 241026 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21209144 is about 4605.3386411859. The cubic root of 21209144 is about 276.8052865775.

Adding to 21209144 its reverse (44190212), we get a palindrome (65399356).

The spelling of 21209144 in words is "twenty-one million, two hundred nine thousand, one hundred forty-four".