19999813 has 4 divisors (see below), whose sum is σ = 20224620. Its totient is φ = 19775008.

The previous prime is 19999789. The next prime is 19999817. The reversal of 19999813 is 31899991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31899991 = 1181 ⋅27011.

It can be written as a sum of positive squares in 2 ways, for example, as 8282884 + 11716929 = 2878^2 + 3423^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19999813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19999817) 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, 112270 + ... + 112447.

It is an arithmetic number, because the mean of its divisors is an integer number (5056155).

Almost surely, 2^19999813 is an apocalyptic number.

It is an amenable number.

19999813 is a deficient number, since it is larger than the sum of its proper divisors (224807).

19999813 is an equidigital number, since it uses as much as digits as its factorization.

19999813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224806.

The product of its digits is 157464, while the sum is 49.

The square root of 19999813 is about 4472.1150477151. The cubic root of 19999813 is about 271.4409156634.

The spelling of 19999813 in words is "nineteen million, nine hundred ninety-nine thousand, eight hundred thirteen".