19813813 has 4 divisors (see below), whose sum is σ = 19824748. Its totient is φ = 19802880.

The previous prime is 19813799. The next prime is 19813819. The reversal of 19813813 is 31831891.

It is a happy number.

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.

It can be written as a sum of positive squares in 2 ways, for example, as 2566404 + 17247409 = 1602^2 + 4153^2 .

It is a cyclic number.

It is not a de Polignac number, because 19813813 - 2⁹ = 19813301 is a prime.

It is a super-3 number, since 3×19813813³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19813819) 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, 2028 + ... + 6613.

It is an arithmetic number, because the mean of its divisors is an integer number (4956187).

Almost surely, 2^19813813 is an apocalyptic number.

It is an amenable number.

19813813 is a deficient number, since it is larger than the sum of its proper divisors (10935).

19813813 is an equidigital number, since it uses as much as digits as its factorization.

19813813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10934.

The product of its digits is 5184, while the sum is 34.

The square root of 19813813 is about 4451.2709421018. The cubic root of 19813813 is about 270.5968187990.

The spelling of 19813813 in words is "nineteen million, eight hundred thirteen thousand, eight hundred thirteen".