19681813 has 4 divisors (see below), whose sum is σ = 20537568. Its totient is φ = 18826060.

The previous prime is 19681789. The next prime is 19681841. The reversal of 19681813 is 31818691.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 19681813 - 2⁹ = 19681301 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 (19681913) 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, 427843 + ... + 427888.

It is an arithmetic number, because the mean of its divisors is an integer number (5134392).

Almost surely, 2^19681813 is an apocalyptic number.

It is an amenable number.

19681813 is a deficient number, since it is larger than the sum of its proper divisors (855755).

19681813 is an equidigital number, since it uses as much as digits as its factorization.

19681813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 855754.

The product of its digits is 10368, while the sum is 37.

The square root of 19681813 is about 4436.4189387388. The cubic root of 19681813 is about 269.9945723646.

The spelling of 19681813 in words is "nineteen million, six hundred eighty-one thousand, eight hundred thirteen".