81704626657 has 4 divisors (see below), whose sum is σ = 82622656260. Its totient is φ = 80786597056.

The previous prime is 81704626639. The next prime is 81704626669. The reversal of 81704626657 is 75662640718.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16651063521 + 65053563136 = 129039^2 + 255056^2 .

It is a cyclic number.

It is not a de Polignac number, because 81704626657 - 2¹⁹ = 81704102369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81704606657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 459014668 + ... + 459014845.

It is an arithmetic number, because the mean of its divisors is an integer number (20655664065).

Almost surely, 2^81704626657 is an apocalyptic number.

It is an amenable number.

81704626657 is a deficient number, since it is larger than the sum of its proper divisors (918029603).

81704626657 is an equidigital number, since it uses as much as digits as its factorization.

81704626657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 918029602.

The product of its (nonzero) digits is 3386880, while the sum is 52.

The spelling of 81704626657 in words is "eighty-one billion, seven hundred four million, six hundred twenty-six thousand, six hundred fifty-seven".