82121208742561 has 8 divisors (see below), whose sum is σ = 84953565239400. Its totient is φ = 79288891624320.

The previous prime is 82121208742541. The next prime is 82121208742577. The reversal of 82121208742561 is 16524780212128.

It can be written as a sum of positive squares in 4 ways, for example, as 9818822250000 + 72302386492561 = 3133500^2 + 8503081^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 82121208742561 - 2¹⁷ = 82121208611489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (82121208742501) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5570410 + ... + 13973971.

It is an arithmetic number, because the mean of its divisors is an integer number (10619195654925).

Almost surely, 2^{82121208742561} is an apocalyptic number.

It is an amenable number.

82121208742561 is a deficient number, since it is larger than the sum of its proper divisors (2832356496839).

82121208742561 is a wasteful number, since it uses less digits than its factorization.

82121208742561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19689299.

The product of its (nonzero) digits is 860160, while the sum is 49.

Adding to 82121208742561 its reverse (16524780212128), we get a palindrome (98645988954689).

The spelling of 82121208742561 in words is "eighty-two trillion, one hundred twenty-one billion, two hundred eight million, seven hundred forty-two thousand, five hundred sixty-one".