1817123981 has 2 divisors, whose sum is σ = 1817123982. Its totient is φ = 1817123980.

The previous prime is 1817123953. The next prime is 1817124013. The reversal of 1817123981 is 1893217181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1489188100 + 327935881 = 38590^2 + 18109^2 .

It is an emirp because it is prime and its reverse (1893217181) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1817123981 is a prime.

It is a super-2 number, since 2×1817123981² = 6603879124650576722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1817123911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 908561990 + 908561991.

It is an arithmetic number, because the mean of its divisors is an integer number (908561991).

Almost surely, 2^1817123981 is an apocalyptic number.

It is an amenable number.

1817123981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1817123981 is an equidigital number, since it uses as much as digits as its factorization.

1817123981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 41.

The square root of 1817123981 is about 42627.7372258955. The cubic root of 1817123981 is about 1220.2856943122.

The spelling of 1817123981 in words is "one billion, eight hundred seventeen million, one hundred twenty-three thousand, nine hundred eighty-one".