21551444 has 24 divisors (see below), whose sum is σ = 40075560. Its totient is φ = 10105856.

The previous prime is 21551441. The next prime is 21551449. The reversal of 21551444 is 44415512.

It can be written as a sum of positive squares in 4 ways, for example, as 280900 + 21270544 = 530^2 + 4612^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551441) by changing a digit.

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, 37592 + ... + 38160.

It is an arithmetic number, because the mean of its divisors is an integer number (1669815).

Almost surely, 2^21551444 is an apocalyptic number.

It is an amenable number.

21551444 is a deficient number, since it is larger than the sum of its proper divisors (18524116).

21551444 is a wasteful number, since it uses less digits than its factorization.

21551444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1147 (or 1145 counting only the distinct ones).

The product of its digits is 3200, while the sum is 26.

The square root of 21551444 is about 4642.3532825497. The cubic root of 21551444 is about 278.2864910553.

Adding to 21551444 its reverse (44415512), we get a palindrome (65966956).

The spelling of 21551444 in words is "twenty-one million, five hundred fifty-one thousand, four hundred forty-four".