1881391 has 2 divisors, whose sum is σ = 1881392. Its totient is φ = 1881390.

The previous prime is 1881389. The next prime is 1881401. The reversal of 1881391 is 1931881.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1881391 - 2¹ = 1881389 is a prime.

Together with 1881389, 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 (1881311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 940695 + 940696.

It is an arithmetic number, because the mean of its divisors is an integer number (940696).

2^1881391 is an apocalyptic number.

1881391 is the 868-th centered pentagonal number.

1881391 is a deficient number, since it is larger than the sum of its proper divisors (1).

1881391 is an equidigital number, since it uses as much as digits as its factorization.

1881391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 31.

The square root of 1881391 is about 1371.6380717959. The cubic root of 1881391 is about 123.4505476033.

The spelling of 1881391 in words is "one million, eight hundred eighty-one thousand, three hundred ninety-one".