21638800 has 60 divisors (see below), whose sum is σ = 53139456. Its totient is φ = 8464000.

The previous prime is 21638797. The next prime is 21638801. The reversal of 21638800 is 883612.

It is not an unprimeable number, because it can be changed into a prime (21638801) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18225 + ... + 19375.

Almost surely, 2^21638800 is an apocalyptic number.

21638800 is a gapful number since it is divisible by the number (20) 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 21638800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26569728).

21638800 is an abundant number, since it is smaller than the sum of its proper divisors (31500656).

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

21638800 is a wasteful number, since it uses less digits than its factorization.

21638800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1216 (or 1205 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 21638800 is about 4651.7523579830. The cubic root of 21638800 is about 278.6619836467.

Adding to 21638800 its product of nonzero digits (2304), we get a square (21641104 = 4652²).

The spelling of 21638800 in words is "twenty-one million, six hundred thirty-eight thousand, eight hundred".