1288621991 has 2 divisors, whose sum is σ = 1288621992. Its totient is φ = 1288621990.

The previous prime is 1288621937. The next prime is 1288622029. The reversal of 1288621991 is 1991268821.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1288621991 - 2¹⁰ = 1288620967 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1288621091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 644310995 + 644310996.

It is an arithmetic number, because the mean of its divisors is an integer number (644310996).

Almost surely, 2^1288621991 is an apocalyptic number.

1288621991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1288621991 is an equidigital number, since it uses as much as digits as its factorization.

1288621991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 124416, while the sum is 47.

The square root of 1288621991 is about 35897.3813947480. The cubic root of 1288621991 is about 1088.1994770023.

The spelling of 1288621991 in words is "one billion, two hundred eighty-eight million, six hundred twenty-one thousand, nine hundred ninety-one".