81787681 has 2 divisors, whose sum is σ = 81787682. Its totient is φ = 81787680.

The previous prime is 81787633. The next prime is 81787687. The reversal of 81787681 is 18678718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 47389456 + 34398225 = 6884^2 + 5865^2 .

It is a cyclic number.

It is not a de Polignac number, because 81787681 - 2¹⁵ = 81754913 is a prime.

It is a super-2 number, since 2×81787681² = 13378449526715522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81787687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40893840 + 40893841.

It is an arithmetic number, because the mean of its divisors is an integer number (40893841).

Almost surely, 2^81787681 is an apocalyptic number.

It is an amenable number.

81787681 is a deficient number, since it is larger than the sum of its proper divisors (1).

81787681 is an equidigital number, since it uses as much as digits as its factorization.

81787681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 150528, while the sum is 46.

The square root of 81787681 is about 9043.6541840121. The cubic root of 81787681 is about 434.0728586437.

The spelling of 81787681 in words is "eighty-one million, seven hundred eighty-seven thousand, six hundred eighty-one".