31231221 has 8 divisors (see below), whose sum is σ = 47590464. Its totient is φ = 17846400.

The previous prime is 31231139. The next prime is 31231223. The reversal of 31231221 is 12213213.

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

It is not a de Polignac number, because 31231221 - 2¹⁷ = 31100149 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31231221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31231223) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 743580 + ... + 743621.

It is an arithmetic number, because the mean of its divisors is an integer number (5948808).

Almost surely, 2^31231221 is an apocalyptic number.

It is an amenable number.

31231221 is a deficient number, since it is larger than the sum of its proper divisors (16359243).

31231221 is a wasteful number, since it uses less digits than its factorization.

31231221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1487211.

The product of its digits is 72, while the sum is 15.

The square root of 31231221 is about 5588.4900465152. The cubic root of 31231221 is about 314.9171563449.

Adding to 31231221 its reverse (12213213), we get a palindrome (43444434).

It can be divided in two parts, 3123 and 1221, that multiplied together give a palindrome (3813183).

The spelling of 31231221 in words is "thirty-one million, two hundred thirty-one thousand, two hundred twenty-one".