1561131331 has 2 divisors, whose sum is σ = 1561131332. Its totient is φ = 1561131330.

The previous prime is 1561131329. The next prime is 1561131349. The reversal of 1561131331 is 1331311651.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1561131331 - 2¹ = 1561131329 is a prime.

It is a super-2 number, since 2×1561131331² = 4874262065259663122, which contains 22 as substring.

Together with 1561131329, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 1561131296 and 1561131305.

It is not a weakly prime, because it can be changed into another prime (1561131431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780565665 + 780565666.

It is an arithmetic number, because the mean of its divisors is an integer number (780565666).

Almost surely, 2^1561131331 is an apocalyptic number.

1561131331 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561131331 is an equidigital number, since it uses as much as digits as its factorization.

1561131331 is an evil number, because the sum of its binary digits is even.

The product of its digits is 810, while the sum is 25.

The square root of 1561131331 is about 39511.1545136307. The cubic root of 1561131331 is about 1160.0582934934.

Adding to 1561131331 its reverse (1331311651), we get a palindrome (2892442982).

The spelling of 1561131331 in words is "one billion, five hundred sixty-one million, one hundred thirty-one thousand, three hundred thirty-one".