21305472 has 64 divisors (see below), whose sum is σ = 57209760. Its totient is φ = 7024640.

The previous prime is 21305461. The next prime is 21305483. The reversal of 21305472 is 27450312.

It is an interprime number because it is at equal distance from previous prime (21305461) and next prime (21305483).

It is a tau number, because it is divible by the number of its divisors (64).

It is a hoax number, since the sum of its digits (24) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

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, 43147 + ... + 43637.

Almost surely, 2^21305472 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 21305472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28604880).

21305472 is an abundant number, since it is smaller than the sum of its proper divisors (35904288).

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

21305472 is a wasteful number, since it uses less digits than its factorization.

21305472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 621 (or 609 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 21305472 is about 4615.7850903178. The cubic root of 21305472 is about 277.2237198312.

Adding to 21305472 its reverse (27450312), we get a palindrome (48755784).

The spelling of 21305472 in words is "twenty-one million, three hundred five thousand, four hundred seventy-two".