21636047 has 4 divisors (see below), whose sum is σ = 22334016. Its totient is φ = 20938080.

The previous prime is 21636037. The next prime is 21636049. The reversal of 21636047 is 74063612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21636047 - 2⁶ = 21635983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21636049) 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 in 3 ways as a sum of consecutive naturals, for example, 348938 + ... + 348999.

It is an arithmetic number, because the mean of its divisors is an integer number (5583504).

Almost surely, 2^21636047 is an apocalyptic number.

21636047 is a deficient number, since it is larger than the sum of its proper divisors (697969).

21636047 is an equidigital number, since it uses as much as digits as its factorization.

21636047 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 697968.

The product of its (nonzero) digits is 6048, while the sum is 29.

The square root of 21636047 is about 4651.4564385792. The cubic root of 21636047 is about 278.6501655395.

Adding to 21636047 its reverse (74063612), we get a palindrome (95699659).

It can be divided in two parts, 216 and 36047, that added together give a palindrome (36263).

The spelling of 21636047 in words is "twenty-one million, six hundred thirty-six thousand, forty-seven".