21405132 has 108 divisors (see below), whose sum is σ = 64676976. Its totient is φ = 5846400.

The previous prime is 21405127. The next prime is 21405149. The reversal of 21405132 is 23150412.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 211882 + ... + 211982.

Almost surely, 2^21405132 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 21405132, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32338488).

21405132 is an abundant number, since it is smaller than the sum of its proper divisors (43271844).

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

21405132 is a wasteful number, since it uses less digits than its factorization.

21405132 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 176 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21405132 is about 4626.5680585073. The cubic root of 21405132 is about 277.6553014315.

Adding to 21405132 its reverse (23150412), we get a palindrome (44555544).

The spelling of 21405132 in words is "twenty-one million, four hundred five thousand, one hundred thirty-two".