21261444 has 12 divisors (see below), whose sum is σ = 49610064. Its totient is φ = 7087144.

The previous prime is 21261433. The next prime is 21261463. The reversal of 21261444 is 44416212.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 885882 + ... + 885905.

It is an arithmetic number, because the mean of its divisors is an integer number (4134172).

Almost surely, 2^21261444 is an apocalyptic number.

It is an amenable number.

21261444 is an abundant number, since it is smaller than the sum of its proper divisors (28348620).

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

21261444 is a wasteful number, since it uses less digits than its factorization.

21261444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1771794 (or 1771792 counting only the distinct ones).

The product of its digits is 1536, while the sum is 24.

The square root of 21261444 is about 4611.0133376515. The cubic root of 21261444 is about 277.0326261491.

Adding to 21261444 its reverse (44416212), we get a palindrome (65677656).

It can be divided in two parts, 2126 and 1444, that added together give a triangular number (3570 = T₈₄).

The spelling of 21261444 in words is "twenty-one million, two hundred sixty-one thousand, four hundred forty-four".