21644152 has 8 divisors (see below), whose sum is σ = 40582800. Its totient is φ = 10822072.

The previous prime is 21644113. The next prime is 21644153. The reversal of 21644152 is 25144612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644153) by changing a digit.

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 as a sum of consecutive naturals, namely, 1352752 + ... + 1352767.

It is an arithmetic number, because the mean of its divisors is an integer number (5072850).

Almost surely, 2^21644152 is an apocalyptic number.

It is an amenable number.

21644152 is a deficient number, since it is larger than the sum of its proper divisors (18938648).

21644152 is a wasteful number, since it uses less digits than its factorization.

21644152 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2705525 (or 2705521 counting only the distinct ones).

The product of its digits is 1920, while the sum is 25.

The square root of 21644152 is about 4652.3275894975. The cubic root of 21644152 is about 278.6849559002.

Adding to 21644152 its reverse (25144612), we get a palindrome (46788764).

The spelling of 21644152 in words is "twenty-one million, six hundred forty-four thousand, one hundred fifty-two".