3943681681 has 4 divisors (see below), whose sum is σ = 3943971892. Its totient is φ = 3943391472.

The previous prime is 3943681663. The next prime is 3943681699. The reversal of 3943681681 is 1861863493.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (3943681663) and next prime (3943681699).

It can be written as a sum of positive squares in 2 ways, for example, as 1053651600 + 2890030081 = 32460^2 + 53759^2 .

It is a cyclic number.

It is not a de Polignac number, because 3943681681 - 2²⁷ = 3809463953 is a prime.

It is a super-2 number, since 2×3943681681² = 31105250402109971522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3943681601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 123666 + ... + 152251.

It is an arithmetic number, because the mean of its divisors is an integer number (985992973).

Almost surely, 2^3943681681 is an apocalyptic number.

It is an amenable number.

3943681681 is a deficient number, since it is larger than the sum of its proper divisors (290211).

3943681681 is a wasteful number, since it uses less digits than its factorization.

3943681681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 290210.

The product of its digits is 746496, while the sum is 49.

The square root of 3943681681 is about 62798.7394857572. The cubic root of 3943681681 is about 1579.9158317872.

The spelling of 3943681681 in words is "three billion, nine hundred forty-three million, six hundred eighty-one thousand, six hundred eighty-one".