21816648 has 128 divisors (see below), whose sum is σ = 70963200. Its totient is φ = 6080832.

The previous prime is 21816647. The next prime is 21816689. The reversal of 21816648 is 84661812.

21816648 is a `hidden beast` number, since 2 + 1 + 8 + 1 + 6 + 648 = 666.

It is a super-2 number, since 2×21816648² = 951932259911808, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

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

It is not an unprimeable number, because it can be changed into a prime (21816647) 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 31 ways as a sum of consecutive naturals, for example, 70911 + ... + 71217.

It is an arithmetic number, because the mean of its divisors is an integer number (554400).

Almost surely, 2^21816648 is an apocalyptic number.

21816648 is a gapful number since it is divisible by the number (28) 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 21816648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35481600).

21816648 is an abundant number, since it is smaller than the sum of its proper divisors (49146552).

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

21816648 is a wasteful number, since it uses less digits than its factorization.

21816648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 376 (or 366 counting only the distinct ones).

The product of its digits is 18432, while the sum is 36.

The square root of 21816648 is about 4670.8294766562. The cubic root of 21816648 is about 279.4233369811.

The spelling of 21816648 in words is "twenty-one million, eight hundred sixteen thousand, six hundred forty-eight".