21040000 has 80 divisors (see below), whose sum is σ = 52576920. Its totient is φ = 8384000.

The previous prime is 21039989. The next prime is 21040001. The reversal of 21040000 is 4012.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040001) by changing a digit.

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 9 ways as a sum of consecutive naturals, for example, 79869 + ... + 80131.

Almost surely, 2^21040000 is an apocalyptic number.

21040000 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 21040000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26288460).

21040000 is an abundant number, since it is smaller than the sum of its proper divisors (31536920).

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

21040000 is an frugal number, since it uses more digits than its factorization.

21040000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297 (or 270 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 7.

The square root of 21040000 is about 4586.9379764719. The cubic root of 21040000 is about 276.0674763257.

Adding to 21040000 its reverse (4012), we get a palindrome (21044012).

The spelling of 21040000 in words is "twenty-one million, forty thousand".