21438648 has 128 divisors (see below), whose sum is σ = 74304000. Its totient is φ = 5564160.

The previous prime is 21438647. The next prime is 21438673. The reversal of 21438648 is 84683412.

21438648 is a `hidden beast` number, since 2 + 1 + 4 + 3 + 8 + 648 = 666.

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 a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21438647) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15988 + ... + 17276.

It is an arithmetic number, because the mean of its divisors is an integer number (580500).

Almost surely, 2^21438648 is an apocalyptic number.

21438648 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 21438648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37152000).

21438648 is an abundant number, since it is smaller than the sum of its proper divisors (52865352).

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

21438648 is a wasteful number, since it uses less digits than its factorization.

21438648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1322 (or 1312 counting only the distinct ones).

The product of its digits is 36864, while the sum is 36.

The square root of 21438648 is about 4630.1887650505. The cubic root of 21438648 is about 277.8001427444.

The spelling of 21438648 in words is "twenty-one million, four hundred thirty-eight thousand, six hundred forty-eight".