61780120015 has 4 divisors (see below), whose sum is σ = 74136144024. Its totient is φ = 49424096008.

The previous prime is 61780119991. The next prime is 61780120021. The reversal of 61780120015 is 51002108716.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 61780120015 - 2³⁵ = 27420381647 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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, 6178011997 + ... + 6178012006.

It is an arithmetic number, because the mean of its divisors is an integer number (18534036006).

Almost surely, 2^61780120015 is an apocalyptic number.

61780120015 is a deficient number, since it is larger than the sum of its proper divisors (12356024009).

61780120015 is a wasteful number, since it uses less digits than its factorization.

61780120015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12356024008.

The product of its (nonzero) digits is 3360, while the sum is 31.

The spelling of 61780120015 in words is "sixty-one billion, seven hundred eighty million, one hundred twenty thousand, fifteen".