1978866785 has 16 divisors (see below), whose sum is σ = 2759875200. Its totient is φ = 1333936896.

The previous prime is 1978866761. The next prime is 1978866787. The reversal of 1978866785 is 5876688791.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1978866785 - 2²⁰ = 1977818209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1978866787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 477080 + ... + 481209.

It is an arithmetic number, because the mean of its divisors is an integer number (172492200).

Almost surely, 2^1978866785 is an apocalyptic number.

It is an amenable number.

1978866785 is a deficient number, since it is larger than the sum of its proper divisors (781008415).

1978866785 is an equidigital number, since it uses as much as digits as its factorization.

1978866785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 958360.

The product of its digits is 40642560, while the sum is 65.

The square root of 1978866785 is about 44484.4555434817. The cubic root of 1978866785 is about 1255.4676299479.

The spelling of 1978866785 in words is "one billion, nine hundred seventy-eight million, eight hundred sixty-six thousand, seven hundred eighty-five".