31361221 has 4 divisors (see below), whose sum is σ = 31561132. Its totient is φ = 31161312.

The previous prime is 31361219. The next prime is 31361227. The reversal of 31361221 is 12216313.

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 15249025 + 16112196 = 3905^2 + 4014^2 .

It is a cyclic number.

It is not a de Polignac number, because 31361221 - 2¹ = 31361219 is a prime.

It is a super-2 number, since 2×31361221² = 1967052365221682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31361227) 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, 99720 + ... + 100033.

It is an arithmetic number, because the mean of its divisors is an integer number (7890283).

Almost surely, 2^31361221 is an apocalyptic number.

It is an amenable number.

31361221 is a deficient number, since it is larger than the sum of its proper divisors (199911).

31361221 is a wasteful number, since it uses less digits than its factorization.

31361221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199910.

The product of its digits is 216, while the sum is 19.

The square root of 31361221 is about 5600.1090167960. The cubic root of 31361221 is about 315.3534991754.

Adding to 31361221 its reverse (12216313), we get a palindrome (43577534).

The spelling of 31361221 in words is "thirty-one million, three hundred sixty-one thousand, two hundred twenty-one".