31315217 has 4 divisors (see below), whose sum is σ = 31326516. Its totient is φ = 31303920.

The previous prime is 31315201. The next prime is 31315231. The reversal of 31315217 is 71251313.

It is a Cunningham number, because it is equal to 5596²+1.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 8667136 + 22648081 = 2944^2 + 4759^2 .

It is a cyclic number.

It is not a de Polignac number, because 31315217 - 2⁴ = 31315201 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31315192 and 31315201.

It is not an unprimeable number, because it can be changed into a prime (31315247) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1667 + ... + 8087.

It is an arithmetic number, because the mean of its divisors is an integer number (7831629).

Almost surely, 2^31315217 is an apocalyptic number.

It is an amenable number.

31315217 is a deficient number, since it is larger than the sum of its proper divisors (11299).

31315217 is an equidigital number, since it uses as much as digits as its factorization.

31315217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11298.

The product of its digits is 630, while the sum is 23.

The square root of 31315217 is about 5596.0000893495. Note that the first 4 decimals coincide. The cubic root of 31315217 is about 315.1992256126.

The spelling of 31315217 in words is "thirty-one million, three hundred fifteen thousand, two hundred seventeen".