21636356 has 48 divisors (see below), whose sum is σ = 45384192. Its totient is φ = 8832000.

The previous prime is 21636347. The next prime is 21636361. The reversal of 21636356 is 65363612.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53756 + ... + 54156.

It is an arithmetic number, because the mean of its divisors is an integer number (945504).

Almost surely, 2^21636356 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 21636356, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22692096).

21636356 is an abundant number, since it is smaller than the sum of its proper divisors (23747836).

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

21636356 is a wasteful number, since it uses less digits than its factorization.

21636356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 500 (or 498 counting only the distinct ones).

The product of its digits is 19440, while the sum is 32.

The square root of 21636356 is about 4651.4896538636. The cubic root of 21636356 is about 278.6514920679.

Adding to 21636356 its reverse (65363612), we get a palindrome (86999968).

The spelling of 21636356 in words is "twenty-one million, six hundred thirty-six thousand, three hundred fifty-six".