21531144 has 32 divisors (see below), whose sum is σ = 54846720. Its totient is φ = 7041216.

The previous prime is 21531127. The next prime is 21531149. The reversal of 21531144 is 44113512.

It is a self number, because there is not a number n which added to its sum of digits gives 21531144.

It is not an unprimeable number, because it can be changed into a prime (21531149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7192 + ... + 9735.

It is an arithmetic number, because the mean of its divisors is an integer number (1713960).

Almost surely, 2^21531144 is an apocalyptic number.

21531144 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21531144 is an abundant number, since it is smaller than the sum of its proper divisors (33315576).

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

21531144 is a wasteful number, since it uses less digits than its factorization.

21531144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16989 (or 16985 counting only the distinct ones).

The product of its digits is 480, while the sum is 21.

The square root of 21531144 is about 4640.1663763275. The cubic root of 21531144 is about 278.1990879340.

Adding to 21531144 its reverse (44113512), we get a palindrome (65644656).

The spelling of 21531144 in words is "twenty-one million, five hundred thirty-one thousand, one hundred forty-four".