1978842857 has 6 divisors (see below), whose sum is σ = 2095439598. Its totient is φ = 1862267712.

The previous prime is 1978842793. The next prime is 1978842907. The reversal of 1978842857 is 7582488791.

It can be written as a sum of positive squares in 3 ways, for example, as 443692096 + 1535150761 = 21064^2 + 39181^2 .

It is not a de Polignac number, because 1978842857 - 2⁶ = 1978842793 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1978842796 and 1978842805.

It is not an unprimeable number, because it can be changed into a prime (1978841857) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 178019 + ... + 188807.

It is an arithmetic number, because the mean of its divisors is an integer number (349239933).

Almost surely, 2^1978842857 is an apocalyptic number.

1978842857 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

It is an amenable number.

1978842857 is a deficient number, since it is larger than the sum of its proper divisors (116596741).

1978842857 is an frugal number, since it uses more digits than its factorization.

1978842857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21595 (or 10806 counting only the distinct ones).

The product of its digits is 9031680, while the sum is 59.

The square root of 1978842857 is about 44484.1865947889. The cubic root of 1978842857 is about 1255.4625696526.

The spelling of 1978842857 in words is "one billion, nine hundred seventy-eight million, eight hundred forty-two thousand, eight hundred fifty-seven".