81899806477 has 2 divisors, whose sum is σ = 81899806478. Its totient is φ = 81899806476.

The previous prime is 81899806463. The next prime is 81899806481. The reversal of 81899806477 is 77460899818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81373838121 + 525968356 = 285261^2 + 22934^2 .

It is a cyclic number.

It is not a de Polignac number, because 81899806477 - 2¹¹ = 81899804429 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81899806277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40949903238 + 40949903239.

It is an arithmetic number, because the mean of its divisors is an integer number (40949903239).

Almost surely, 2^81899806477 is an apocalyptic number.

It is an amenable number.

81899806477 is a deficient number, since it is larger than the sum of its proper divisors (1).

81899806477 is an equidigital number, since it uses as much as digits as its factorization.

81899806477 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48771072, while the sum is 67.

The spelling of 81899806477 in words is "eighty-one billion, eight hundred ninety-nine million, eight hundred six thousand, four hundred seventy-seven".