1681343981 has 2 divisors, whose sum is σ = 1681343982. Its totient is φ = 1681343980.

The previous prime is 1681343941. The next prime is 1681344017. The reversal of 1681343981 is 1893431861.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1424383081 + 256960900 = 37741^2 + 16030^2 .

It is a cyclic number.

It is not a de Polignac number, because 1681343981 - 2¹⁸ = 1681081837 is a prime.

It is a super-2 number, since 2×1681343981² = 5653835164889856722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1681343921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 840671990 + 840671991.

It is an arithmetic number, because the mean of its divisors is an integer number (840671991).

Almost surely, 2^1681343981 is an apocalyptic number.

It is an amenable number.

1681343981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1681343981 is an equidigital number, since it uses as much as digits as its factorization.

1681343981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 124416, while the sum is 44.

The square root of 1681343981 is about 41004.1946756670. The cubic root of 1681343981 is about 1189.1013107461.

The spelling of 1681343981 in words is "one billion, six hundred eighty-one million, three hundred forty-three thousand, nine hundred eighty-one".