1678778991 has 24 divisors (see below), whose sum is σ = 2634877440. Its totient is φ = 1026075600.

The previous prime is 1678778909. The next prime is 1678779007. The reversal of 1678778991 is 1998778761.

It is not a de Polignac number, because 1678778991 - 2¹⁰ = 1678777967 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1678778291) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 153045 + ... + 163646.

It is an arithmetic number, because the mean of its divisors is an integer number (109786560).

Almost surely, 2^1678778991 is an apocalyptic number.

1678778991 is a deficient number, since it is larger than the sum of its proper divisors (956098449).

1678778991 is a wasteful number, since it uses less digits than its factorization.

1678778991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316747 (or 316744 counting only the distinct ones).

The product of its digits is 10668672, while the sum is 63.

The square root of 1678778991 is about 40972.9055718532. The cubic root of 1678778991 is about 1188.4963214590.

The spelling of 1678778991 in words is "one billion, six hundred seventy-eight million, seven hundred seventy-eight thousand, nine hundred ninety-one".