981978891 has 4 divisors (see below), whose sum is σ = 1309305192. Its totient is φ = 654652592.

The previous prime is 981978883. The next prime is 981978923. The reversal of 981978891 is 198879189.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 198879189 = 3 ⋅66293063.

It is a cyclic number.

It is not a de Polignac number, because 981978891 - 2³ = 981978883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (981938891) 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 3 ways as a sum of consecutive naturals, for example, 163663146 + ... + 163663151.

It is an arithmetic number, because the mean of its divisors is an integer number (327326298).

Almost surely, 2^981978891 is an apocalyptic number.

981978891 is a deficient number, since it is larger than the sum of its proper divisors (327326301).

981978891 is a wasteful number, since it uses less digits than its factorization.

981978891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 327326300.

The product of its digits is 2612736, while the sum is 60.

The square root of 981978891 is about 31336.5424225456. The cubic root of 981978891 is about 993.9565135147.

The spelling of 981978891 in words is "nine hundred eighty-one million, nine hundred seventy-eight thousand, eight hundred ninety-one".