31216221 has 24 divisors (see below), whose sum is σ = 49533120. Its totient is φ = 18855936.

The previous prime is 31216193. The next prime is 31216243. The reversal of 31216221 is 12261213.

It is not a de Polignac number, because 31216221 - 2¹³ = 31208029 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31216194 and 31216203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31216291) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36 + ... + 7901.

It is an arithmetic number, because the mean of its divisors is an integer number (2063880).

Almost surely, 2^31216221 is an apocalyptic number.

It is an amenable number.

31216221 is a deficient number, since it is larger than the sum of its proper divisors (18316899).

31216221 is a wasteful number, since it uses less digits than its factorization.

31216221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7985 (or 7982 counting only the distinct ones).

The product of its digits is 144, while the sum is 18.

The square root of 31216221 is about 5587.1478412514. The cubic root of 31216221 is about 314.8667312291.

Adding to 31216221 its reverse (12261213), we get a palindrome (43477434).

The spelling of 31216221 in words is "thirty-one million, two hundred sixteen thousand, two hundred twenty-one".