81981761 has 2 divisors, whose sum is σ = 81981762. Its totient is φ = 81981760.

The previous prime is 81981719. The next prime is 81981773. The reversal of 81981761 is 16718918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74718736 + 7263025 = 8644^2 + 2695^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81981761 is a prime.

It is a super-2 number, since 2×81981761² = 13442018273322242, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81981791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40990880 + 40990881.

It is an arithmetic number, because the mean of its divisors is an integer number (40990881).

Almost surely, 2^81981761 is an apocalyptic number.

It is an amenable number.

81981761 is a deficient number, since it is larger than the sum of its proper divisors (1).

81981761 is an equidigital number, since it uses as much as digits as its factorization.

81981761 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 81981761 is about 9054.3780018287. The cubic root of 81981761 is about 434.4159352136.

The spelling of 81981761 in words is "eighty-one million, nine hundred eighty-one thousand, seven hundred sixty-one".