21264444 has 72 divisors (see below), whose sum is σ = 56504448. Its totient is φ = 6991920.

The previous prime is 21264427. The next prime is 21264449. The reversal of 21264444 is 44446212.

It is a happy number.

21264444 is a `hidden beast` number, since 2 + 12 + 644 + 4 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21264449) 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 23 ways as a sum of consecutive naturals, for example, 127249 + ... + 127415.

It is an arithmetic number, because the mean of its divisors is an integer number (784784).

Almost surely, 2^21264444 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 21264444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28252224).

21264444 is an abundant number, since it is smaller than the sum of its proper divisors (35240004).

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

21264444 is a wasteful number, since it uses less digits than its factorization.

21264444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 317 (or 303 counting only the distinct ones).

The product of its digits is 6144, while the sum is 27.

The square root of 21264444 is about 4611.3386342796. The cubic root of 21264444 is about 277.0456553487.

The spelling of 21264444 in words is "twenty-one million, two hundred sixty-four thousand, four hundred forty-four".