21453444 has 48 divisors (see below), whose sum is σ = 55901440. Its totient is φ = 7115040.

The previous prime is 21453433. The next prime is 21453449. The reversal of 21453444 is 44435412.

It is a happy number.

21453444 is a `hidden beast` number, since 214 + 5 + 3 + 444 = 666.

It is a super-2 number, since 2×21453444² = 920500518922272, which contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (21453449) 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 15 ways as a sum of consecutive naturals, for example, 28902 + ... + 29634.

Almost surely, 2^21453444 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 21453444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27950720).

21453444 is an abundant number, since it is smaller than the sum of its proper divisors (34447996).

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

21453444 is a wasteful number, since it uses less digits than its factorization.

21453444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1017 (or 1009 counting only the distinct ones).

The product of its digits is 7680, while the sum is 27.

The square root of 21453444 is about 4631.7862644988. The cubic root of 21453444 is about 277.8640364764.

Adding to 21453444 its reverse (44435412), we get a palindrome (65888856).

The spelling of 21453444 in words is "twenty-one million, four hundred fifty-three thousand, four hundred forty-four".