78681533007661 has 4 divisors (see below), whose sum is σ = 81394689318300. Its totient is φ = 75968376697024.

The previous prime is 78681533007617. The next prime is 78681533007703. The reversal of 78681533007661 is 16670033518687.

It is a happy number.

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 59421064752036 + 19260468255625 = 7708506^2 + 4388675^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78681533007661 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 78681533007661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78681533007461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1356578155276 + ... + 1356578155333.

It is an arithmetic number, because the mean of its divisors is an integer number (20348672329575).

Almost surely, 2^{78681533007661} is an apocalyptic number.

It is an amenable number.

78681533007661 is a deficient number, since it is larger than the sum of its proper divisors (2713156310639).

78681533007661 is a wasteful number, since it uses less digits than its factorization.

78681533007661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2713156310638.

The product of its (nonzero) digits is 30481920, while the sum is 61.

The spelling of 78681533007661 in words is "seventy-eight trillion, six hundred eighty-one billion, five hundred thirty-three million, seven thousand, six hundred sixty-one".