21315144 has 64 divisors (see below), whose sum is σ = 57153600. Its totient is φ = 6600704.

The previous prime is 21315139. The next prime is 21315163. The reversal of 21315144 is 44151312.

It is a self number, because there is not a number n which added to its sum of digits gives 21315144.

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 15 ways as a sum of consecutive naturals, for example, 36019 + ... + 36605.

It is an arithmetic number, because the mean of its divisors is an integer number (893025).

Almost surely, 2^21315144 is an apocalyptic number.

21315144 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21315144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28576800).

21315144 is an abundant number, since it is smaller than the sum of its proper divisors (35838456).

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

21315144 is a wasteful number, since it uses less digits than its factorization.

21315144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 702 (or 698 counting only the distinct ones).

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

The square root of 21315144 is about 4616.8326805289. The cubic root of 21315144 is about 277.2656637064.

Adding to 21315144 its reverse (44151312), we get a palindrome (65466456).

The spelling of 21315144 in words is "twenty-one million, three hundred fifteen thousand, one hundred forty-four".