81821182657 has 2 divisors, whose sum is σ = 81821182658. Its totient is φ = 81821182656.

The previous prime is 81821182621. The next prime is 81821182679. The reversal of 81821182657 is 75628112818.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81801148081 + 20034576 = 286009^2 + 4476^2 .

It is a cyclic number.

It is not a de Polignac number, because 81821182657 - 2²⁷ = 81686964929 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81821182657.

It is not a weakly prime, because it can be changed into another prime (81821182607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40910591328 + 40910591329.

It is an arithmetic number, because the mean of its divisors is an integer number (40910591329).

Almost surely, 2^81821182657 is an apocalyptic number.

It is an amenable number.

81821182657 is a deficient number, since it is larger than the sum of its proper divisors (1).

81821182657 is an equidigital number, since it uses as much as digits as its factorization.

81821182657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 430080, while the sum is 49.

The spelling of 81821182657 in words is "eighty-one billion, eight hundred twenty-one million, one hundred eighty-two thousand, six hundred fifty-seven".