31536221 has 4 divisors (see below), whose sum is σ = 31548444. Its totient is φ = 31524000.

The previous prime is 31536203. The next prime is 31536223. The reversal of 31536221 is 12263513.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 13980121 + 17556100 = 3739^2 + 4190^2 .

It is a cyclic number.

It is not a de Polignac number, because 31536221 - 2¹⁴ = 31519837 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 (31536223) 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, 560 + ... + 7961.

It is an arithmetic number, because the mean of its divisors is an integer number (7887111).

Almost surely, 2^31536221 is an apocalyptic number.

It is an amenable number.

31536221 is a deficient number, since it is larger than the sum of its proper divisors (12223).

31536221 is an equidigital number, since it uses as much as digits as its factorization.

31536221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12222.

The product of its digits is 1080, while the sum is 23.

The square root of 31536221 is about 5615.7119762324. The cubic root of 31536221 is about 315.9389837060.

Adding to 31536221 its reverse (12263513), we get a palindrome (43799734).

The spelling of 31536221 in words is "thirty-one million, five hundred thirty-six thousand, two hundred twenty-one".