1778318661665 has 96 divisors (see below), whose sum is σ = 2820583221120. Its totient is φ = 1063895648256.

The previous prime is 1778318661607. The next prime is 1778318661667. The reversal of 1778318661665 is 5661668138771.

It is not a de Polignac number, because 1778318661665 - 2⁶ = 1778318661601 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (65).

It is not an unprimeable number, because it can be changed into a prime (1778318661667) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 26169062 + ... + 26236928.

It is an arithmetic number, because the mean of its divisors is an integer number (29381075220).

Almost surely, 2^{1778318661665} is an apocalyptic number.

It is an amenable number.

1778318661665 is a deficient number, since it is larger than the sum of its proper divisors (1042264559455).

1778318661665 is a wasteful number, since it uses less digits than its factorization.

1778318661665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68351 (or 68344 counting only the distinct ones).

The product of its digits is 60963840, while the sum is 65.

The spelling of 1778318661665 in words is "one trillion, seven hundred seventy-eight billion, three hundred eighteen million, six hundred sixty-one thousand, six hundred sixty-five".