9781391 has 2 divisors, whose sum is σ = 9781392. Its totient is φ = 9781390.

The previous prime is 9781379. The next prime is 9781451. The reversal of 9781391 is 1931879.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 9781391 - 2¹⁰ = 9780367 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9781361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4890695 + 4890696.

It is an arithmetic number, because the mean of its divisors is an integer number (4890696).

Almost surely, 2^9781391 is an apocalyptic number.

9781391 is a deficient number, since it is larger than the sum of its proper divisors (1).

9781391 is an equidigital number, since it uses as much as digits as its factorization.

9781391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13608, while the sum is 38.

The square root of 9781391 is about 3127.5215426916. The cubic root of 9781391 is about 213.8619586066.

The spelling of 9781391 in words is "nine million, seven hundred eighty-one thousand, three hundred ninety-one".