21453408 has 72 divisors (see below), whose sum is σ = 61516728. Its totient is φ = 7091712.

The previous prime is 21453401. The next prime is 21453427. The reversal of 21453408 is 80435412.

It is a tau number, because it is divible by the number of its divisors (72).

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21453401) 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 11 ways as a sum of consecutive naturals, for example, 46716 + ... + 47172.

It is an arithmetic number, because the mean of its divisors is an integer number (854399).

Almost surely, 2^21453408 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 21453408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30758364).

21453408 is an abundant number, since it is smaller than the sum of its proper divisors (40063320).

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

21453408 is a wasteful number, since it uses less digits than its factorization.

21453408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636 (or 625 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21453408 is about 4631.7823783075. The cubic root of 21453408 is about 277.8638810528.

The spelling of 21453408 in words is "twenty-one million, four hundred fifty-three thousand, four hundred eight".