21605144 has 16 divisors (see below), whose sum is σ = 44192520. Its totient is φ = 9820480.

The previous prime is 21605123. The next prime is 21605159. The reversal of 21605144 is 44150612.

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 122669 + ... + 122844.

Almost surely, 2^21605144 is an apocalyptic number.

It is an amenable number.

21605144 is an abundant number, since it is smaller than the sum of its proper divisors (22587376).

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

21605144 is a wasteful number, since it uses less digits than its factorization.

21605144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245530 (or 245526 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21605144 is about 4648.1333887917. The cubic root of 21605144 is about 278.5174359777.

Adding to 21605144 its reverse (44150612), we get a palindrome (65755756).

The spelling of 21605144 in words is "twenty-one million, six hundred five thousand, one hundred forty-four".