21005104 has 20 divisors (see below), whose sum is σ = 42011200. Its totient is φ = 10163520.

The previous prime is 21005087. The next prime is 21005111. The reversal of 21005104 is 40150012.

21005104 is an admirable number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20679 + ... + 21670.

It is an arithmetic number, because the mean of its divisors is an integer number (2100560).

Almost surely, 2^21005104 is an apocalyptic number.

It is an amenable number.

21005104 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21005104 is a wasteful number, since it uses less digits than its factorization.

21005104 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42388 (or 42382 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21005104 is about 4583.1325531780. The cubic root of 21005104 is about 275.9147674926.

Adding to 21005104 its reverse (40150012), we get a palindrome (61155116).

The spelling of 21005104 in words is "twenty-one million, five thousand, one hundred four".