21404440 has 32 divisors (see below), whose sum is σ = 48420000. Its totient is φ = 8515584.

The previous prime is 21404437. The next prime is 21404459. The reversal of 21404440 is 4440412.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 6616 + ... + 9304.

It is an arithmetic number, because the mean of its divisors is an integer number (1513125).

Almost surely, 2^21404440 is an apocalyptic number.

21404440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21404440 is an abundant number, since it is smaller than the sum of its proper divisors (27015560).

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

21404440 is a wasteful number, since it uses less digits than its factorization.

21404440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2899 (or 2895 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 19.

The square root of 21404440 is about 4626.4932724473. The cubic root of 21404440 is about 277.6523093213.

Adding to 21404440 its reverse (4440412), we get a palindrome (25844852).

The spelling of 21404440 in words is "twenty-one million, four hundred four thousand, four hundred forty".