1681618181 has 2 divisors, whose sum is σ = 1681618182. Its totient is φ = 1681618180.

The previous prime is 1681618163. The next prime is 1681618187. The reversal of 1681618181 is 1818161861.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1647629281 + 33988900 = 40591^2 + 5830^2 .

It is an emirp because it is prime and its reverse (1818161861) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 1818191891 and 1981918181.

It is a cyclic number.

It is not a de Polignac number, because 1681618181 - 2⁶ = 1681618117 is a prime.

It is a super-2 number, since 2×1681618181² = 5655679413339497522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1681618187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 840809090 + 840809091.

It is an arithmetic number, because the mean of its divisors is an integer number (840809091).

Almost surely, 2^1681618181 is an apocalyptic number.

It is an amenable number.

1681618181 is a deficient number, since it is larger than the sum of its proper divisors (1).

1681618181 is an equidigital number, since it uses as much as digits as its factorization.

1681618181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18432, while the sum is 41.

The square root of 1681618181 is about 41007.5380997202. The cubic root of 1681618181 is about 1189.1659482940.

The spelling of 1681618181 in words is "one billion, six hundred eighty-one million, six hundred eighteen thousand, one hundred eighty-one".