31291221 has 8 divisors (see below), whose sum is σ = 44931040. Its totient is φ = 19256112.

The previous prime is 31291219. The next prime is 31291279. The reversal of 31291221 is 12219213.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 31291221 - 2¹ = 31291219 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 (31291021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 401131 + ... + 401208.

It is an arithmetic number, because the mean of its divisors is an integer number (5616380).

Almost surely, 2^31291221 is an apocalyptic number.

It is an amenable number.

31291221 is a deficient number, since it is larger than the sum of its proper divisors (13639819).

31291221 is a wasteful number, since it uses less digits than its factorization.

31291221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 802355.

The product of its digits is 216, while the sum is 21.

The square root of 31291221 is about 5593.8556470470. The cubic root of 31291221 is about 315.1186955054.

The spelling of 31291221 in words is "thirty-one million, two hundred ninety-one thousand, two hundred twenty-one".