81651198779 has 2 divisors, whose sum is σ = 81651198780. Its totient is φ = 81651198778.

The previous prime is 81651198743. The next prime is 81651198817. The reversal of 81651198779 is 97789115618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81651198779 - 2⁸ = 81651198523 is a prime.

It is not a weakly prime, because it can be changed into another prime (81651195779) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40825599389 + 40825599390.

It is an arithmetic number, because the mean of its divisors is an integer number (40825599390).

Almost surely, 2^81651198779 is an apocalyptic number.

81651198779 is a deficient number, since it is larger than the sum of its proper divisors (1).

81651198779 is an equidigital number, since it uses as much as digits as its factorization.

81651198779 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7620480, while the sum is 62.

The spelling of 81651198779 in words is "eighty-one billion, six hundred fifty-one million, one hundred ninety-eight thousand, seven hundred seventy-nine".