21806536 has 8 divisors (see below), whose sum is σ = 40887270. Its totient is φ = 10903264.

The previous prime is 21806527. The next prime is 21806539. The reversal of 21806536 is 63560812.

It can be written as a sum of positive squares in only one way, i.e., 10956100 + 10850436 = 3310^2 + 3294^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 21806498 and 21806507.

It is not an unprimeable number, because it can be changed into a prime (21806539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1362901 + ... + 1362916.

Almost surely, 2^21806536 is an apocalyptic number.

It is an amenable number.

21806536 is a deficient number, since it is larger than the sum of its proper divisors (19080734).

21806536 is a wasteful number, since it uses less digits than its factorization.

21806536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2725823 (or 2725819 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 21806536 is about 4669.7468882157. The cubic root of 21806536 is about 279.3801594738.

The spelling of 21806536 in words is "twenty-one million, eight hundred six thousand, five hundred thirty-six".