78661138337809 has 24 divisors (see below), whose sum is σ = 85409001901440. Its totient is φ = 72413722557696.

The previous prime is 78661138337777. The next prime is 78661138337813. The reversal of 78661138337809 is 90873383116687.

It is not a de Polignac number, because 78661138337809 - 2⁵ = 78661138337777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78661138337819) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13656922 + ... + 18542755.

It is an arithmetic number, because the mean of its divisors is an integer number (3558708412560).

Almost surely, 2^{78661138337809} is an apocalyptic number.

78661138337809 is a gapful number since it is divisible by the number (79) formed by its first and last digit.

It is an amenable number.

78661138337809 is a deficient number, since it is larger than the sum of its proper divisors (6747863563631).

78661138337809 is a wasteful number, since it uses less digits than its factorization.

78661138337809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32199897 (or 32199880 counting only the distinct ones).

The product of its (nonzero) digits is 219469824, while the sum is 70.

The spelling of 78661138337809 in words is "seventy-eight trillion, six hundred sixty-one billion, one hundred thirty-eight million, three hundred thirty-seven thousand, eight hundred nine".