21523284 has 18 divisors (see below), whose sum is σ = 54406170. Its totient is φ = 7174416.

The previous prime is 21523283. The next prime is 21523339. The reversal of 21523284 is 48232512.

It can be written as a sum of positive squares in only one way, i.e., 11410884 + 10112400 = 3378^2 + 3180^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523283) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 298899 + ... + 298970.

It is an arithmetic number, because the mean of its divisors is an integer number (3022565).

Almost surely, 2^21523284 is an apocalyptic number.

It is an amenable number.

21523284 is an abundant number, since it is smaller than the sum of its proper divisors (32882886).

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

21523284 is a wasteful number, since it uses less digits than its factorization.

21523284 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 597879 (or 597874 counting only the distinct ones).

The product of its digits is 3840, while the sum is 27.

The square root of 21523284 is about 4639.3193466283. The cubic root of 21523284 is about 278.1652313809.

Adding to 21523284 its reverse (48232512), we get a palindrome (69755796).

The spelling of 21523284 in words is "twenty-one million, five hundred twenty-three thousand, two hundred eighty-four".