1981663 has 2 divisors, whose sum is σ = 1981664. Its totient is φ = 1981662.

The previous prime is 1981649. The next prime is 1981667. The reversal of 1981663 is 3661891.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1981663 - 2⁵ = 1981631 is a prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990831 + 990832.

It is an arithmetic number, because the mean of its divisors is an integer number (990832).

2^1981663 is an apocalyptic number.

1981663 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981663 is an equidigital number, since it uses as much as digits as its factorization.

1981663 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7776, while the sum is 34.

The square root of 1981663 is about 1407.7155252394. The cubic root of 1981663 is about 125.6058693012.

The spelling of 1981663 in words is "one million, nine hundred eighty-one thousand, six hundred sixty-three".