21126556 has 48 divisors (see below), whose sum is σ = 43666560. Its totient is φ = 8838720.

The previous prime is 21126551. The next prime is 21126569. The reversal of 21126556 is 65562112.

It is a super-3 number, since 3×21126556³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21126551) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30591 + ... + 31273.

It is an arithmetic number, because the mean of its divisors is an integer number (909720).

Almost surely, 2^21126556 is an apocalyptic number.

It is an amenable number.

21126556 is an abundant number, since it is smaller than the sum of its proper divisors (22540004).

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

21126556 is a wasteful number, since it uses less digits than its factorization.

21126556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 754 (or 752 counting only the distinct ones).

The product of its digits is 3600, while the sum is 28.

The square root of 21126556 is about 4596.3633450805. The cubic root of 21126556 is about 276.4455277154.

Adding to 21126556 its reverse (65562112), we get a palindrome (86688668).

Subtracting 21126556 from its reverse (65562112), we obtain a square (44435556 = 6666²).

It can be divided in two parts, 2112 and 6556, that added together give a palindrome (8668).

The spelling of 21126556 in words is "twenty-one million, one hundred twenty-six thousand, five hundred fifty-six".