21210444 has 48 divisors (see below), whose sum is σ = 55266400. Its totient is φ = 7034688.

The previous prime is 21210433. The next prime is 21210461. The reversal of 21210444 is 44401212.

21210444 is a `hidden beast` number, since 212 + 10 + 444 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 29562 + ... + 30270.

Almost surely, 2^21210444 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21210444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27633200).

21210444 is an abundant number, since it is smaller than the sum of its proper divisors (34055956).

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

21210444 is a wasteful number, since it uses less digits than its factorization.

21210444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 999 (or 991 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 21210444 is about 4605.4797795669. The cubic root of 21210444 is about 276.8109419923.

Adding to 21210444 its reverse (44401212), we get a palindrome (65611656).

The spelling of 21210444 in words is "twenty-one million, two hundred ten thousand, four hundred forty-four".