1981687 has 2 divisors, whose sum is σ = 1981688. Its totient is φ = 1981686.

The previous prime is 1981669. The next prime is 1981691. The reversal of 1981687 is 7861891.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981687 is a prime.

It is a Chen prime.

It is an Ulam number.

1981687 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990843 + 990844.

It is an arithmetic number, because the mean of its divisors is an integer number (990844).

2^1981687 is an apocalyptic number.

1981687 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981687 is an equidigital number, since it uses as much as digits as its factorization.

1981687 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24192, while the sum is 40.

The square root of 1981687 is about 1407.7240496631. The cubic root of 1981687 is about 125.6063763718.

The spelling of 1981687 in words is "one million, nine hundred eighty-one thousand, six hundred eighty-seven".