21638448 has 80 divisors (see below), whose sum is σ = 66905440. Its totient is φ = 6656256.

The previous prime is 21638431. The next prime is 21638479. The reversal of 21638448 is 84483612.

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 an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3690 + ... + 7542.

It is an arithmetic number, because the mean of its divisors is an integer number (836318).

Almost surely, 2^21638448 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 21638448, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33452720).

21638448 is an abundant number, since it is smaller than the sum of its proper divisors (45266992).

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

21638448 is a wasteful number, since it uses less digits than its factorization.

21638448 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3883 (or 3871 counting only the distinct ones).

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

The square root of 21638448 is about 4651.7145226250. The cubic root of 21638448 is about 278.6604726333.

The spelling of 21638448 in words is "twenty-one million, six hundred thirty-eight thousand, four hundred forty-eight".