999778811 has 4 divisors (see below), whose sum is σ = 999880032. Its totient is φ = 999677592.

The previous prime is 999778807. The next prime is 999778867. The reversal of 999778811 is 118877999.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 118877999 = 2887 ⋅41177.

It is a cyclic number.

It is not a de Polignac number, because 999778811 - 2² = 999778807 is a prime.

It is a Duffinian number.

It is a zygodrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (999778111) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33971 + ... + 56156.

It is an arithmetic number, because the mean of its divisors is an integer number (249970008).

Almost surely, 2^999778811 is an apocalyptic number.

999778811 is a deficient number, since it is larger than the sum of its proper divisors (101221).

999778811 is a wasteful number, since it uses less digits than its factorization.

999778811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101220.

The product of its digits is 2286144, while the sum is 59.

The square root of 999778811 is about 31619.2791031042. The cubic root of 999778811 is about 999.9262648966.

The spelling of 999778811 in words is "nine hundred ninety-nine million, seven hundred seventy-eight thousand, eight hundred eleven".