31331561 has 4 divisors (see below), whose sum is σ = 33174612. Its totient is φ = 29488512.

The previous prime is 31331557. The next prime is 31331569. The reversal of 31331561 is 16513313.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 27931225 + 3400336 = 5285^2 + 1844^2 .

It is a cyclic number.

It is not a de Polignac number, because 31331561 - 2² = 31331557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31331569) 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, 921500 + ... + 921533.

It is an arithmetic number, because the mean of its divisors is an integer number (8293653).

Almost surely, 2^31331561 is an apocalyptic number.

It is an amenable number.

31331561 is a deficient number, since it is larger than the sum of its proper divisors (1843051).

31331561 is a wasteful number, since it uses less digits than its factorization.

31331561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1843050.

The product of its digits is 810, while the sum is 23.

The square root of 31331561 is about 5597.4602276390. The cubic root of 31331561 is about 315.2540522077.

Adding to 31331561 its reverse (16513313), we get a palindrome (47844874).

The spelling of 31331561 in words is "thirty-one million, three hundred thirty-one thousand, five hundred sixty-one".