21306444 has 12 divisors (see below), whose sum is σ = 49715064. Its totient is φ = 7102144.

The previous prime is 21306433. The next prime is 21306473. The reversal of 21306444 is 44460312.

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

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, 887757 + ... + 887780.

It is an arithmetic number, because the mean of its divisors is an integer number (4142922).

Almost surely, 2^21306444 is an apocalyptic number.

It is an amenable number.

21306444 is an abundant number, since it is smaller than the sum of its proper divisors (28408620).

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

21306444 is a wasteful number, since it uses less digits than its factorization.

21306444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1775544 (or 1775542 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 21306444 is about 4615.8903799809. The cubic root of 21306444 is about 277.2279356082.

Adding to 21306444 its reverse (44460312), we get a palindrome (65766756).

The spelling of 21306444 in words is "twenty-one million, three hundred six thousand, four hundred forty-four".