81814981 has 2 divisors, whose sum is σ = 81814982. Its totient is φ = 81814980.

The previous prime is 81814937. The next prime is 81815011. The reversal of 81814981 is 18941818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72760900 + 9054081 = 8530^2 + 3009^2 .

It is a cyclic number.

It is not a de Polignac number, because 81814981 - 2¹¹ = 81812933 is a prime.

It is a super-2 number, since 2×81814981² = 13387382232060722, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81814781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40907490 + 40907491.

It is an arithmetic number, because the mean of its divisors is an integer number (40907491).

Almost surely, 2^81814981 is an apocalyptic number.

It is an amenable number.

81814981 is a deficient number, since it is larger than the sum of its proper divisors (1).

81814981 is an equidigital number, since it uses as much as digits as its factorization.

81814981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18432, while the sum is 40.

The square root of 81814981 is about 9045.1634037202. The cubic root of 81814981 is about 434.1211498234.

The spelling of 81814981 in words is "eighty-one million, eight hundred fourteen thousand, nine hundred eighty-one".