21050556 has 48 divisors (see below), whose sum is σ = 54754560. Its totient is φ = 6255360.

The previous prime is 21050527. The next prime is 21050567. The reversal of 21050556 is 65505012.

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 15 ways as a sum of consecutive naturals, for example, 1161 + ... + 6591.

It is an arithmetic number, because the mean of its divisors is an integer number (1140720).

Almost surely, 2^21050556 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 21050556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27377280).

21050556 is an abundant number, since it is smaller than the sum of its proper divisors (33704004).

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

21050556 is a wasteful number, since it uses less digits than its factorization.

21050556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5474 (or 5472 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 24.

The square root of 21050556 is about 4588.0884908641. The cubic root of 21050556 is about 276.1136373057.

Adding to 21050556 its reverse (65505012), we get a palindrome (86555568).

The spelling of 21050556 in words is "twenty-one million, fifty thousand, five hundred fifty-six".