21618072 has 96 divisors (see below), whose sum is σ = 68140800. Its totient is φ = 6063552.

The previous prime is 21618059. The next prime is 21618109. The reversal of 21618072 is 27081612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 29373 + ... + 30099.

It is an arithmetic number, because the mean of its divisors is an integer number (709800).

Almost surely, 2^21618072 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 21618072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34070400).

21618072 is an abundant number, since it is smaller than the sum of its proper divisors (46522728).

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

21618072 is a wasteful number, since it uses less digits than its factorization.

21618072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 805 (or 798 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21618072 is about 4649.5238465890. The cubic root of 21618072 is about 278.5729776189.

Adding to 21618072 its reverse (27081612), we get a palindrome (48699684).

The spelling of 21618072 in words is "twenty-one million, six hundred eighteen thousand, seventy-two".