636243221 has 4 divisors (see below), whose sum is σ = 639540012. Its totient is φ = 632946432.

The previous prime is 636243211. The next prime is 636243233. The reversal of 636243221 is 122342636.

636243221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in 2 ways, for example, as 268140625 + 368102596 = 16375^2 + 19186^2 .

It is a cyclic number.

It is not a de Polignac number, because 636243221 - 2²² = 632048917 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (636243211) 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, 1648106 + ... + 1648491.

It is an arithmetic number, because the mean of its divisors is an integer number (159885003).

Almost surely, 2^636243221 is an apocalyptic number.

It is an amenable number.

636243221 is a deficient number, since it is larger than the sum of its proper divisors (3296791).

636243221 is a wasteful number, since it uses less digits than its factorization.

636243221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3296790.

The product of its digits is 10368, while the sum is 29.

The square root of 636243221 is about 25223.8621348912. The cubic root of 636243221 is about 860.0843711167.

Adding to 636243221 its reverse (122342636), we get a palindrome (758585857).

The spelling of 636243221 in words is "six hundred thirty-six million, two hundred forty-three thousand, two hundred twenty-one".