21816000 has 224 divisors, whose sum is σ = 80832960. Its totient is φ = 5760000.

The previous prime is 21815999. The next prime is 21816031. The reversal of 21816000 is 61812.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 215950 + ... + 216050.

Almost surely, 2^21816000 is an apocalyptic number.

21816000 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 21816000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40416480).

21816000 is an abundant number, since it is smaller than the sum of its proper divisors (59016960).

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

21816000 is a wasteful number, since it uses less digits than its factorization.

21816000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137 (or 111 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21816000 is about 4670.7601094469. The cubic root of 21816000 is about 279.4205704682.

Adding to 21816000 its reverse (61812), we get a palindrome (21877812).

The spelling of 21816000 in words is "twenty-one million, eight hundred sixteen thousand".