31171221 has 12 divisors (see below), whose sum is σ = 45147648. Its totient is φ = 20724264.

The previous prime is 31171207. The next prime is 31171223. The reversal of 31171221 is 12217113.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-31171221 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31171194 and 31171203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31171223) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1075 + ... + 7968.

It is an arithmetic number, because the mean of its divisors is an integer number (3762304).

Almost surely, 2^31171221 is an apocalyptic number.

It is an amenable number.

31171221 is a deficient number, since it is larger than the sum of its proper divisors (13976427).

31171221 is a wasteful number, since it uses less digits than its factorization.

31171221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9432 (or 9429 counting only the distinct ones).

The product of its digits is 84, while the sum is 18.

The square root of 31171221 is about 5583.1192894295. The cubic root of 31171221 is about 314.7153588935.

Adding to 31171221 its reverse (12217113), we get a palindrome (43388334).

The spelling of 31171221 in words is "thirty-one million, one hundred seventy-one thousand, two hundred twenty-one".