31913561 has 2 divisors, whose sum is σ = 31913562. Its totient is φ = 31913560.

The previous prime is 31913509. The next prime is 31913569. The reversal of 31913561 is 16531913.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28955161 + 2958400 = 5381^2 + 1720^2 .

It is an emirp because it is prime and its reverse (16531913) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31913561 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (31913569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15956780 + 15956781.

It is an arithmetic number, because the mean of its divisors is an integer number (15956781).

Almost surely, 2^31913561 is an apocalyptic number.

It is an amenable number.

31913561 is a deficient number, since it is larger than the sum of its proper divisors (1).

31913561 is an equidigital number, since it uses as much as digits as its factorization.

31913561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2430, while the sum is 29.

The square root of 31913561 is about 5649.2088826667. The cubic root of 31913561 is about 317.1940914498.

The spelling of 31913561 in words is "thirty-one million, nine hundred thirteen thousand, five hundred sixty-one".