1305531991 has 2 divisors, whose sum is σ = 1305531992. Its totient is φ = 1305531990.

The previous prime is 1305531989. The next prime is 1305532001. The reversal of 1305531991 is 1991355031.

It is a weak prime.

It is an emirp because it is prime and its reverse (1991355031) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1305531991 - 2¹ = 1305531989 is a prime.

Together with 1305531989, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1305531991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1305531091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 652765995 + 652765996.

It is an arithmetic number, because the mean of its divisors is an integer number (652765996).

Almost surely, 2^1305531991 is an apocalyptic number.

1305531991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1305531991 is an equidigital number, since it uses as much as digits as its factorization.

1305531991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18225, while the sum is 37.

The square root of 1305531991 is about 36132.1462274247. The cubic root of 1305531991 is about 1092.9387886356.

The spelling of 1305531991 in words is "one billion, three hundred five million, five hundred thirty-one thousand, nine hundred ninety-one".