21405324 has 48 divisors (see below), whose sum is σ = 52935680. Its totient is φ = 6713280.

The previous prime is 21405313. The next prime is 21405337. The reversal of 21405324 is 42350412.

It is a self number, because there is not a number n which added to its sum of digits gives 21405324.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50634 + ... + 51054.

Almost surely, 2^21405324 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 21405324, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26467840).

21405324 is an abundant number, since it is smaller than the sum of its proper divisors (31530356).

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

21405324 is a wasteful number, since it uses less digits than its factorization.

21405324 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 670 (or 668 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21405324 is about 4626.5888081825. The cubic root of 21405324 is about 277.6561316009.

Adding to 21405324 its reverse (42350412), we get a palindrome (63755736).

It can be divided in two parts, 2 and 1405324, that added together give a triangular number (1405326 = T₁₆₇₆).

The spelling of 21405324 in words is "twenty-one million, four hundred five thousand, three hundred twenty-four".