21551324 has 24 divisors (see below), whose sum is σ = 39223296. Its totient is φ = 10350000.

The previous prime is 21551323. The next prime is 21551351. The reversal of 21551324 is 42315512.

It is a Smith number, since the sum of its digits (23) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21551324.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551323) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18149 + ... + 19299.

It is an arithmetic number, because the mean of its divisors is an integer number (1634304).

Almost surely, 2^21551324 is an apocalyptic number.

It is an amenable number.

21551324 is a deficient number, since it is larger than the sum of its proper divisors (17671972).

21551324 is a wasteful number, since it uses less digits than its factorization.

21551324 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1337 (or 1335 counting only the distinct ones).

The product of its digits is 1200, while the sum is 23.

The square root of 21551324 is about 4642.3403580522. The cubic root of 21551324 is about 278.2859745479.

Adding to 21551324 its reverse (42315512), we get a palindrome (63866836).

The spelling of 21551324 in words is "twenty-one million, five hundred fifty-one thousand, three hundred twenty-four".