21453784 has 48 divisors (see below), whose sum is σ = 45486000. Its totient is φ = 9472320.

The previous prime is 21453769. The next prime is 21453787. The reversal of 21453784 is 48735412.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21453787) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35517 + ... + 36115.

It is an arithmetic number, because the mean of its divisors is an integer number (947625).

Almost surely, 2^21453784 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 21453784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22743000).

21453784 is an abundant number, since it is smaller than the sum of its proper divisors (24032216).

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

21453784 is a wasteful number, since it uses less digits than its factorization.

21453784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 664 (or 649 counting only the distinct ones).

The product of its digits is 26880, while the sum is 34.

The square root of 21453784 is about 4631.8229672560. The cubic root of 21453784 is about 277.8655043568.

It can be divided in two parts, 2145 and 3784, that added together give a square (5929 = 77²).

The spelling of 21453784 in words is "twenty-one million, four hundred fifty-three thousand, seven hundred eighty-four".