21616224 has 96 divisors (see below), whose sum is σ = 68302080. Its totient is φ = 5847552.

The previous prime is 21616213. The next prime is 21616237. The reversal of 21616224 is 42261612.

It is a tau number, because it is divible by the number of its divisors (96).

It is a super-2 number, since 2×21616224² = 934522280036352, which contains 22 as substring.

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

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21616194 and 21616203.

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 15 ways as a sum of consecutive naturals, for example, 11922 + ... + 13614.

It is an arithmetic number, because the mean of its divisors is an integer number (711480).

Almost surely, 2^21616224 is an apocalyptic number.

21616224 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21616224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34151040).

21616224 is an abundant number, since it is smaller than the sum of its proper divisors (46685856).

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

21616224 is a wasteful number, since it uses less digits than its factorization.

21616224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1732 (or 1724 counting only the distinct ones).

The product of its digits is 1152, while the sum is 24.

The square root of 21616224 is about 4649.3251123147. The cubic root of 21616224 is about 278.5650395454.

Adding to 21616224 its reverse (42261612), we get a palindrome (63877836).

It can be divided in two parts, 2161 and 6224, that added together give a triangular number (8385 = T₁₂₉).

The spelling of 21616224 in words is "twenty-one million, six hundred sixteen thousand, two hundred twenty-four".