31213121 has 8 divisors (see below), whose sum is σ = 31881864. Its totient is φ = 30551040.

The previous prime is 31213109. The next prime is 31213129. The reversal of 31213121 is 12131213.

It can be written as a sum of positive squares in 4 ways, for example, as 255025 + 30958096 = 505^2 + 5564^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31213121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31213096 and 31213105.

It is not an unprimeable number, because it can be changed into a prime (31213129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8441 + ... + 11561.

It is an arithmetic number, because the mean of its divisors is an integer number (3985233).

Almost surely, 2^31213121 is an apocalyptic number.

It is an amenable number.

31213121 is a deficient number, since it is larger than the sum of its proper divisors (668743).

31213121 is a wasteful number, since it uses less digits than its factorization.

31213121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3331.

The product of its digits is 36, while the sum is 14.

The square root of 31213121 is about 5586.8704119569. The cubic root of 31213121 is about 314.8563080245.

Adding to 31213121 its reverse (12131213), we get a palindrome (43344334).

It can be divided in two parts, 31213 and 121, that multiplied together give a palindrome (3776773).

The spelling of 31213121 in words is "thirty-one million, two hundred thirteen thousand, one hundred twenty-one".