81977894899 has 2 divisors, whose sum is σ = 81977894900. Its totient is φ = 81977894898.

The previous prime is 81977894857. The next prime is 81977894903. The reversal of 81977894899 is 99849877918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81977894899 - 2⁷ = 81977894771 is a prime.

It is not a weakly prime, because it can be changed into another prime (81977804899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40988947449 + 40988947450.

It is an arithmetic number, because the mean of its divisors is an integer number (40988947450).

Almost surely, 2^81977894899 is an apocalyptic number.

81977894899 is a deficient number, since it is larger than the sum of its proper divisors (1).

81977894899 is an equidigital number, since it uses as much as digits as its factorization.

81977894899 is an evil number, because the sum of its binary digits is even.

The product of its digits is 658409472, while the sum is 79.

The spelling of 81977894899 in words is "eighty-one billion, nine hundred seventy-seven million, eight hundred ninety-four thousand, eight hundred ninety-nine".