81966331 has 2 divisors, whose sum is σ = 81966332. Its totient is φ = 81966330.

The previous prime is 81966329. The next prime is 81966341. The reversal of 81966331 is 13366918.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81966331 - 2¹ = 81966329 is a prime.

It is a super-2 number, since 2×81966331² = 13436958835203122, which contains 22 as substring.

Together with 81966329, it forms a pair of twin primes.

It is equal to p_4777561 and since 81966331 and 4777561 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81966301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40983165 + 40983166.

It is an arithmetic number, because the mean of its divisors is an integer number (40983166).

Almost surely, 2^81966331 is an apocalyptic number.

81966331 is a deficient number, since it is larger than the sum of its proper divisors (1).

81966331 is an equidigital number, since it uses as much as digits as its factorization.

81966331 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23328, while the sum is 37.

The square root of 81966331 is about 9053.5258877412. The cubic root of 81966331 is about 434.3886793201.

The spelling of 81966331 in words is "eighty-one million, nine hundred sixty-six thousand, three hundred thirty-one".