21056436 has 96 divisors (see below), whose sum is σ = 57859200. Its totient is φ = 6695136.

The previous prime is 21056401. The next prime is 21056437. The reversal of 21056436 is 63465012.

21056436 is a `hidden beast` number, since 2 + 10 + 5 + 643 + 6 = 666.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056437) 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 31 ways as a sum of consecutive naturals, for example, 253651 + ... + 253733.

It is an arithmetic number, because the mean of its divisors is an integer number (602700).

Almost surely, 2^21056436 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 21056436, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28929600).

21056436 is an abundant number, since it is smaller than the sum of its proper divisors (36802764).

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

21056436 is an equidigital number, since it uses as much as digits as its factorization.

21056436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137 (or 117 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 21056436 is about 4588.7292358560. The cubic root of 21056436 is about 276.1393436267.

The spelling of 21056436 in words is "twenty-one million, fifty-six thousand, four hundred thirty-six".