21136556 has 12 divisors (see below), whose sum is σ = 42273168. Its totient is φ = 9058512.

The previous prime is 21136553. The next prime is 21136571. The reversal of 21136556 is 65563112.

21136556 is an admirable number.

It is a super-2 number, since 2×21136556² = 893507999082272, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21136553) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 377411 + ... + 377466.

It is an arithmetic number, because the mean of its divisors is an integer number (3522764).

Almost surely, 2^21136556 is an apocalyptic number.

It is an amenable number.

21136556 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21136556 is a wasteful number, since it uses less digits than its factorization.

21136556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 754888 (or 754886 counting only the distinct ones).

The product of its digits is 5400, while the sum is 29.

The square root of 21136556 is about 4597.4510329094. The cubic root of 21136556 is about 276.4891382187.

Adding to 21136556 its reverse (65563112), we get a palindrome (86699668).

The spelling of 21136556 in words is "twenty-one million, one hundred thirty-six thousand, five hundred fifty-six".