21104240 has 20 divisors (see below), whose sum is σ = 49067544. Its totient is φ = 8441664.

The previous prime is 21104233. The next prime is 21104243. The reversal of 21104240 is 4240112.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21104243) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 131822 + ... + 131981.

Almost surely, 2^21104240 is an apocalyptic number.

21104240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21104240 is an abundant number, since it is smaller than the sum of its proper divisors (27963304).

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

21104240 is a wasteful number, since it uses less digits than its factorization.

21104240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263816 (or 263810 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21104240 is about 4593.9351323239. The cubic root of 21104240 is about 276.3481568703.

Adding to 21104240 its reverse (4240112), we get a palindrome (25344352).

The spelling of 21104240 in words is "twenty-one million, one hundred four thousand, two hundred forty".