1321738991 has 2 divisors, whose sum is σ = 1321738992. Its totient is φ = 1321738990.

The previous prime is 1321738987. The next prime is 1321738993. The reversal of 1321738991 is 1998371231.

It is a strong prime.

It is an emirp because it is prime and its reverse (1998371231) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1321738991 - 2² = 1321738987 is a prime.

It is a Sophie Germain prime.

Together with 1321738993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1321738993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 660869495 + 660869496.

It is an arithmetic number, because the mean of its divisors is an integer number (660869496).

Almost surely, 2^1321738991 is an apocalyptic number.

1321738991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1321738991 is an equidigital number, since it uses as much as digits as its factorization.

1321738991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 81648, while the sum is 44.

The square root of 1321738991 is about 36355.7284482102. The cubic root of 1321738991 is about 1097.4428177478.

The spelling of 1321738991 in words is "one billion, three hundred twenty-one million, seven hundred thirty-eight thousand, nine hundred ninety-one".