21404444 has 24 divisors (see below), whose sum is σ = 39318048. Its totient is φ = 10176320.

The previous prime is 21404437. The next prime is 21404459. The reversal of 21404444 is 44440412.

It is a Harshad number since it is a multiple of its sum of digits (23).

21404444 is a modest number, since divided by 4444 gives 2140 as remainder.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17534 + ... + 18714.

It is an arithmetic number, because the mean of its divisors is an integer number (1638252).

Almost surely, 2^21404444 is an apocalyptic number.

It is an amenable number.

21404444 is a deficient number, since it is larger than the sum of its proper divisors (17913604).

21404444 is a wasteful number, since it uses less digits than its factorization.

21404444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1405 (or 1403 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 23.

The square root of 21404444 is about 4626.4937047401. The cubic root of 21404444 is about 277.6523266169.

Adding to 21404444 its reverse (44440412), we get a palindrome (65844856).

The spelling of 21404444 in words is "twenty-one million, four hundred four thousand, four hundred forty-four".