21126784 has 128 divisors (see below), whose sum is σ = 54345600. Its totient is φ = 7962624.

The previous prime is 21126773. The next prime is 21126827. The reversal of 21126784 is 48762112.

It is a tau number, because it is divible by the number of its divisors (128).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 289372 + ... + 289444.

It is an arithmetic number, because the mean of its divisors is an integer number (424575).

Almost surely, 2^21126784 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 21126784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27172800).

21126784 is an abundant number, since it is smaller than the sum of its proper divisors (33218816).

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

21126784 is a wasteful number, since it uses less digits than its factorization.

21126784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130 (or 118 counting only the distinct ones).

The product of its digits is 5376, while the sum is 31.

The square root of 21126784 is about 4596.3881472304. The cubic root of 21126784 is about 276.4465221882.

Adding to 21126784 its reverse (48762112), we get a palindrome (69888896).

The spelling of 21126784 in words is "twenty-one million, one hundred twenty-six thousand, seven hundred eighty-four".