78516534171661 has 4 divisors (see below), whose sum is σ = 80431571590524. Its totient is φ = 76601496752800.

The previous prime is 78516534171623. The next prime is 78516534171697. The reversal of 78516534171661 is 16617143561587.

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 7049901177225 + 71466632994436 = 2655165^2 + 8453794^2 .

It is a cyclic number.

It is not a de Polignac number, because 78516534171661 - 2¹⁹ = 78516533647373 is a prime.

It is a super-3 number, since 3×78516534171661³ (a number of 43 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

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 78516534171661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78516534171161) 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, 957518709370 + ... + 957518709451.

It is an arithmetic number, because the mean of its divisors is an integer number (20107892897631).

Almost surely, 2^{78516534171661} is an apocalyptic number.

It is an amenable number.

78516534171661 is a deficient number, since it is larger than the sum of its proper divisors (1915037418863).

78516534171661 is a wasteful number, since it uses less digits than its factorization.

78516534171661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1915037418862.

The product of its digits is 25401600, while the sum is 61.

The spelling of 78516534171661 in words is "seventy-eight trillion, five hundred sixteen billion, five hundred thirty-four million, one hundred seventy-one thousand, six hundred sixty-one".