1371991 has 2 divisors, whose sum is σ = 1371992. Its totient is φ = 1371990.

The previous prime is 1371989. The next prime is 1372027. The reversal of 1371991 is 1991731.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1371991 - 2¹ = 1371989 is a prime.

Together with 1371989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1371911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 685995 + 685996.

It is an arithmetic number, because the mean of its divisors is an integer number (685996).

2^1371991 is an apocalyptic number.

1371991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1371991 is an equidigital number, since it uses as much as digits as its factorization.

1371991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1701, while the sum is 31.

The square root of 1371991 is about 1171.3201953352. The cubic root of 1371991 is about 111.1178306677.

The spelling of 1371991 in words is "one million, three hundred seventy-one thousand, nine hundred ninety-one".