21918000 has 160 divisors (see below), whose sum is σ = 76370112. Its totient is φ = 5376000.

The previous prime is 21917999. The next prime is 21918007. The reversal of 21918000 is 81912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21918007) 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, 77860 + ... + 78140.

Almost surely, 2^21918000 is an apocalyptic number.

21918000 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 21918000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38185056).

21918000 is an abundant number, since it is smaller than the sum of its proper divisors (54452112).

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

21918000 is a wasteful number, since it uses less digits than its factorization.

21918000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320 (or 304 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 21918000 is about 4681.6663700012. Note that the first 3 decimals coincide. The cubic root of 21918000 is about 279.8553674806.

Adding to 21918000 its reverse (81912), we get a palindrome (21999912).

The spelling of 21918000 in words is "twenty-one million, nine hundred eighteen thousand".