18986813 has 4 divisors (see below), whose sum is σ = 19449948. Its totient is φ = 18523680.

The previous prime is 18986801. The next prime is 18986837. The reversal of 18986813 is 31868981.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31868981 = 179 ⋅178039.

It can be written as a sum of positive squares in 2 ways, for example, as 1026169 + 17960644 = 1013^2 + 4238^2 .

It is a cyclic number.

It is not a de Polignac number, because 18986813 - 2⁴ = 18986797 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 (18986873) 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, 231506 + ... + 231587.

It is an arithmetic number, because the mean of its divisors is an integer number (4862487).

Almost surely, 2^18986813 is an apocalyptic number.

It is an amenable number.

18986813 is a deficient number, since it is larger than the sum of its proper divisors (463135).

18986813 is an equidigital number, since it uses as much as digits as its factorization.

18986813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 463134.

The product of its digits is 82944, while the sum is 44.

The square root of 18986813 is about 4357.3860283431. The cubic root of 18986813 is about 266.7784168783.

The spelling of 18986813 in words is "eighteen million, nine hundred eighty-six thousand, eight hundred thirteen".