1681988081 has 4 divisors (see below), whose sum is σ = 1739987700. Its totient is φ = 1623988464.

The previous prime is 1681988071. The next prime is 1681988093. The reversal of 1681988081 is 1808891861.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 902461681 + 779526400 = 30041^2 + 27920^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1681988081 is a prime.

It is a super-2 number, since 2×1681988081² = 5658167809252125122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1681988071) 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 in 3 ways as a sum of consecutive naturals, for example, 28999766 + ... + 28999823.

It is an arithmetic number, because the mean of its divisors is an integer number (434996925).

Almost surely, 2^1681988081 is an apocalyptic number.

It is an amenable number.

1681988081 is a deficient number, since it is larger than the sum of its proper divisors (57999619).

1681988081 is an equidigital number, since it uses as much as digits as its factorization.

1681988081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57999618.

The product of its (nonzero) digits is 221184, while the sum is 50.

The square root of 1681988081 is about 41012.0479981188. The cubic root of 1681988081 is about 1189.2531342043.

The spelling of 1681988081 in words is "one billion, six hundred eighty-one million, nine hundred eighty-eight thousand, eighty-one".