21531324 has 12 divisors (see below), whose sum is σ = 50239784. Its totient is φ = 7177104.

The previous prime is 21531317. The next prime is 21531337. The reversal of 21531324 is 42313512.

It is a tau number, because it is divible by the number of its divisors (12).

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21531324.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 897127 + ... + 897150.

Almost surely, 2^21531324 is an apocalyptic number.

It is an amenable number.

21531324 is an abundant number, since it is smaller than the sum of its proper divisors (28708460).

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

21531324 is a wasteful number, since it uses less digits than its factorization.

21531324 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1794284 (or 1794282 counting only the distinct ones).

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

The square root of 21531324 is about 4640.1857721432. The cubic root of 21531324 is about 278.1998631784.

Adding to 21531324 its reverse (42313512), we get a palindrome (63844836).

The spelling of 21531324 in words is "twenty-one million, five hundred thirty-one thousand, three hundred twenty-four".