21044940 has 96 divisors (see below), whose sum is σ = 68221440. Its totient is φ = 4747776.

The previous prime is 21044927. The next prime is 21044987. The reversal of 21044940 is 4944012.

It is a self number, because there is not a number n which added to its sum of digits gives 21044940.

It is an unprimeable number.

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, 37099 + ... + 37661.

It is an arithmetic number, because the mean of its divisors is an integer number (710640).

Almost surely, 2^21044940 is an apocalyptic number.

21044940 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 21044940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34110720).

21044940 is an abundant number, since it is smaller than the sum of its proper divisors (47176500).

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

21044940 is a wasteful number, since it uses less digits than its factorization.

21044940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 671 (or 669 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21044940 is about 4587.4764304572. The cubic root of 21044940 is about 276.0890806764.

Adding to 21044940 its reverse (4944012), we get a palindrome (25988952).

It can be divided in two parts, 210 and 44940, that added together give a triangular number (45150 = T₃₀₀).

The spelling of 21044940 in words is "twenty-one million, forty-four thousand, nine hundred forty".