1378137991 has 2 divisors, whose sum is σ = 1378137992. Its totient is φ = 1378137990.

The previous prime is 1378137983. The next prime is 1378138007. The reversal of 1378137991 is 1997318731.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1378137991 - 2³ = 1378137983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1378137931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 689068995 + 689068996.

It is an arithmetic number, because the mean of its divisors is an integer number (689068996).

Almost surely, 2^1378137991 is an apocalyptic number.

1378137991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1378137991 is an equidigital number, since it uses as much as digits as its factorization.

1378137991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 285768, while the sum is 49.

The square root of 1378137991 is about 37123.2809837708. The cubic root of 1378137991 is about 1112.8353213160.

The spelling of 1378137991 in words is "one billion, three hundred seventy-eight million, one hundred thirty-seven thousand, nine hundred ninety-one".