21836556 has 54 divisors (see below), whose sum is σ = 64215060. Its totient is φ = 6238512.

The previous prime is 21836537. The next prime is 21836557. The reversal of 21836556 is 65563812.

21836556 is a `hidden beast` number, since 21 + 83 + 6 + 556 = 666.

It is a super-2 number, since 2×21836556² = 953670355882272, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21836556.

It is not an unprimeable number, because it can be changed into a prime (21836557) 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 17 ways as a sum of consecutive naturals, for example, 4426 + ... + 7953.

Almost surely, 2^21836556 is an apocalyptic number.

It is an amenable number.

21836556 is an abundant number, since it is smaller than the sum of its proper divisors (42378504).

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

21836556 is a wasteful number, since it uses less digits than its factorization.

21836556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12403 (or 12391 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 21836556 is about 4672.9600897076. The cubic root of 21836556 is about 279.5083037248.

The spelling of 21836556 in words is "twenty-one million, eight hundred thirty-six thousand, five hundred fifty-six".