21090444 has 24 divisors (see below), whose sum is σ = 50542128. Its totient is φ = 6840000.

The previous prime is 21090439. The next prime is 21090457. The reversal of 21090444 is 44409012.

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, 23307 + ... + 24194.

It is an arithmetic number, because the mean of its divisors is an integer number (2105922).

Almost surely, 2^21090444 is an apocalyptic number.

It is an amenable number.

21090444 is an abundant number, since it is smaller than the sum of its proper divisors (29451684).

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

21090444 is a wasteful number, since it uses less digits than its factorization.

21090444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47545 (or 47543 counting only the distinct ones).

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

The square root of 21090444 is about 4592.4333419223. The cubic root of 21090444 is about 276.2879267898.

Adding to 21090444 its reverse (44409012), we get a palindrome (65499456).

The spelling of 21090444 in words is "twenty-one million, ninety thousand, four hundred forty-four".