1338957991 has 16 divisors (see below), whose sum is σ = 1561239360. Its totient is φ = 1124570880.

The previous prime is 1338957967. The next prime is 1338958001. The reversal of 1338957991 is 1997598331.

It is a cyclic number.

It is not a de Polignac number, because 1338957991 - 2⁵ = 1338957959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1338957931) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 109035 + ... + 120691.

It is an arithmetic number, because the mean of its divisors is an integer number (97577460).

Almost surely, 2^1338957991 is an apocalyptic number.

1338957991 is a deficient number, since it is larger than the sum of its proper divisors (222281369).

1338957991 is a wasteful number, since it uses less digits than its factorization.

1338957991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11994.

The product of its digits is 1837080, while the sum is 55.

The square root of 1338957991 is about 36591.7749091240. The cubic root of 1338957991 is about 1102.1879292871.

The spelling of 1338957991 in words is "one billion, three hundred thirty-eight million, nine hundred fifty-seven thousand, nine hundred ninety-one".