13991818 has 4 divisors (see below), whose sum is σ = 20987730. Its totient is φ = 6995908.

The previous prime is 13991807. The next prime is 13991821. The reversal of 13991818 is 81819931.

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: 81819931 = 67 ⋅1221193.

It can be written as a sum of positive squares in only one way, i.e., 11377129 + 2614689 = 3373^2 + 1617^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3497953 + ... + 3497956.

Almost surely, 2^13991818 is an apocalyptic number.

13991818 is a deficient number, since it is larger than the sum of its proper divisors (6995912).

13991818 is an equidigital number, since it uses as much as digits as its factorization.

13991818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6995911.

The product of its digits is 15552, while the sum is 40.

The square root of 13991818 is about 3740.5638612380. The cubic root of 13991818 is about 240.9672654012.

The spelling of 13991818 in words is "thirteen million, nine hundred ninety-one thousand, eight hundred eighteen".