1891987 has 2 divisors, whose sum is σ = 1891988. Its totient is φ = 1891986.

The previous prime is 1891969. The next prime is 1891991. The reversal of 1891987 is 7891981.

It is a strong prime.

It is an emirp because it is prime and its reverse (7891981) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1891987 - 2⁷ = 1891859 is a prime.

It is a super-2 number, since 2×1891987² = 7159229616338, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1891907) 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, 945993 + 945994.

It is an arithmetic number, because the mean of its divisors is an integer number (945994).

2^1891987 is an apocalyptic number.

1891987 is a deficient number, since it is larger than the sum of its proper divisors (1).

1891987 is an equidigital number, since it uses as much as digits as its factorization.

1891987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 43.

The square root of 1891987 is about 1375.4951835612. The cubic root of 1891987 is about 123.6818718292.

The spelling of 1891987 in words is "one million, eight hundred ninety-one thousand, nine hundred eighty-seven".