81581446777 has 2 divisors, whose sum is σ = 81581446778. Its totient is φ = 81581446776.

The previous prime is 81581446753. The next prime is 81581446801. The reversal of 81581446777 is 77764418518.

It is a balanced prime because it is at equal distance from previous prime (81581446753) and next prime (81581446801).

It can be written as a sum of positive squares in only one way, i.e., 68432467216 + 13148979561 = 261596^2 + 114669^2 .

It is a cyclic number.

It is not a de Polignac number, because 81581446777 - 2⁷ = 81581446649 is a prime.

It is not a weakly prime, because it can be changed into another prime (81581446717) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40790723388 + 40790723389.

It is an arithmetic number, because the mean of its divisors is an integer number (40790723389).

Almost surely, 2^81581446777 is an apocalyptic number.

It is an amenable number.

81581446777 is a deficient number, since it is larger than the sum of its proper divisors (1).

81581446777 is an equidigital number, since it uses as much as digits as its factorization.

81581446777 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10536960, while the sum is 58.

The spelling of 81581446777 in words is "eighty-one billion, five hundred eighty-one million, four hundred forty-six thousand, seven hundred seventy-seven".