21513324 has 48 divisors (see below), whose sum is σ = 57709568. Its totient is φ = 6110208.

The previous prime is 21513307. The next prime is 21513329. The reversal of 21513324 is 42331512.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a self number, because there is not a number n which added to its sum of digits gives 21513324.

It is not an unprimeable number, because it can be changed into a prime (21513329) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15549 + ... + 16875.

Almost surely, 2^21513324 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21513324, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28854784).

21513324 is an abundant number, since it is smaller than the sum of its proper divisors (36196244).

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

21513324 is a wasteful number, since it uses less digits than its factorization.

21513324 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1534 (or 1532 counting only the distinct ones).

The product of its digits is 720, while the sum is 21.

The square root of 21513324 is about 4638.2457890888. The cubic root of 21513324 is about 278.1223173415.

Adding to 21513324 its reverse (42331512), we get a palindrome (63844836).

The spelling of 21513324 in words is "twenty-one million, five hundred thirteen thousand, three hundred twenty-four".