21326784 has 56 divisors (see below), whose sum is σ = 56772048. Its totient is φ = 7065600.

The previous prime is 21326779. The next prime is 21326807. The reversal of 21326784 is 48762312.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 52984 + ... + 53384.

Almost surely, 2^21326784 is an apocalyptic number.

21326784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21326784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28386024).

21326784 is an abundant number, since it is smaller than the sum of its proper divisors (35445264).

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

21326784 is a wasteful number, since it uses less digits than its factorization.

21326784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 693 (or 683 counting only the distinct ones).

The product of its digits is 16128, while the sum is 33.

The square root of 21326784 is about 4618.0931129634. The cubic root of 21326784 is about 277.3161252472.

Subtracting from 21326784 its product of digits (16128), we obtain a triangular number (21310656 = T₆₅₂₈).

Subtracting 21326784 from its reverse (48762312), we obtain a triangular number (27435528 = T₇₄₀₇).

The spelling of 21326784 in words is "twenty-one million, three hundred twenty-six thousand, seven hundred eighty-four".