1998979823 has 4 divisors (see below), whose sum is σ = 1999232928. Its totient is φ = 1998726720.

The previous prime is 1998979817. The next prime is 1998979859. The reversal of 1998979823 is 3289798991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3289798991 = 61 ⋅53931131.

It is a cyclic number.

It is not a de Polignac number, because 1998979823 - 2²² = 1994785519 is a prime.

It is a super-2 number, since 2×1998979823² = 7991840665522222658, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1998979823.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1998979123) 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, 114311 + ... + 130632.

It is an arithmetic number, because the mean of its divisors is an integer number (499808232).

Almost surely, 2^1998979823 is an apocalyptic number.

1998979823 is a deficient number, since it is larger than the sum of its proper divisors (253105).

1998979823 is an equidigital number, since it uses as much as digits as its factorization.

1998979823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 253104.

The product of its digits is 17635968, while the sum is 65.

The square root of 1998979823 is about 44709.9521695114. The cubic root of 1998979823 is about 1259.7067897140.

The spelling of 1998979823 in words is "one billion, nine hundred ninety-eight million, nine hundred seventy-nine thousand, eight hundred twenty-three".