81677778997 has 2 divisors, whose sum is σ = 81677778998. Its totient is φ = 81677778996.

The previous prime is 81677778989. The next prime is 81677779061. The reversal of 81677778997 is 79987777618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 58080518001 + 23597260996 = 240999^2 + 153614^2 .

It is a cyclic number.

It is not a de Polignac number, because 81677778997 - 2³ = 81677778989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81677778977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40838889498 + 40838889499.

It is an arithmetic number, because the mean of its divisors is an integer number (40838889499).

Almost surely, 2^81677778997 is an apocalyptic number.

It is an amenable number.

81677778997 is a deficient number, since it is larger than the sum of its proper divisors (1).

81677778997 is an equidigital number, since it uses as much as digits as its factorization.

81677778997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 522764928, while the sum is 76.

The spelling of 81677778997 in words is "eighty-one billion, six hundred seventy-seven million, seven hundred seventy-eight thousand, nine hundred ninety-seven".