21001104 has 120 divisors (see below), whose sum is σ = 62674560. Its totient is φ = 6553344.

The previous prime is 21001087. The next prime is 21001117. The reversal of 21001104 is 40110012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 196219 + ... + 196325.

It is an arithmetic number, because the mean of its divisors is an integer number (522288).

Almost surely, 2^21001104 is an apocalyptic number.

21001104 is a gapful number since it is divisible by the number (24) 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 21001104, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31337280).

21001104 is an abundant number, since it is smaller than the sum of its proper divisors (41673456).

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

21001104 is a wasteful number, since it uses less digits than its factorization.

21001104 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197 (or 188 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21001104 is about 4582.6961496482. The cubic root of 21001104 is about 275.8972522396.

Adding to 21001104 its reverse (40110012), we get a palindrome (61111116).

The spelling of 21001104 in words is "twenty-one million, one thousand, one hundred four".