82720517257661 has 4 divisors (see below), whose sum is σ = 82907245288032. Its totient is φ = 82533789227292.

The previous prime is 82720517257589. The next prime is 82720517257663. The reversal of 82720517257661 is 16675271502728.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 82720517257661 - 2¹⁸ = 82720516995517 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 82720517257661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (82720517257663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 93364014521 + ... + 93364015406.

It is an arithmetic number, because the mean of its divisors is an integer number (20726811322008).

Almost surely, 2^{82720517257661} is an apocalyptic number.

It is an amenable number.

82720517257661 is a deficient number, since it is larger than the sum of its proper divisors (186728030371).

82720517257661 is a wasteful number, since it uses less digits than its factorization.

82720517257661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186728030370.

The product of its (nonzero) digits is 19756800, while the sum is 59.

The spelling of 82720517257661 in words is "eighty-two trillion, seven hundred twenty billion, five hundred seventeen million, two hundred fifty-seven thousand, six hundred sixty-one".