21012544 has 112 divisors (see below), whose sum is σ = 52669440. Its totient is φ = 8110080.

The previous prime is 21012533. The next prime is 21012569. The reversal of 21012544 is 44521012.

It is a tau number, because it is divible by the number of its divisors (112).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 236052 + ... + 236140.

Almost surely, 2^21012544 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 21012544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26334720).

21012544 is an abundant number, since it is smaller than the sum of its proper divisors (31656896).

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

21012544 is a wasteful number, since it uses less digits than its factorization.

21012544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156 (or 146 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 21012544 is about 4583.9441532375. The cubic root of 21012544 is about 275.9473399497.

Adding to 21012544 its reverse (44521012), we get a palindrome (65533556).

The spelling of 21012544 in words is "twenty-one million, twelve thousand, five hundred forty-four".