13991815 has 4 divisors (see below), whose sum is σ = 16790184. Its totient is φ = 11193448.

The previous prime is 13991807. The next prime is 13991821. The reversal of 13991815 is 51819931.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 13991815 - 2³ = 13991807 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1399177 + ... + 1399186.

It is an arithmetic number, because the mean of its divisors is an integer number (4197546).

Almost surely, 2^13991815 is an apocalyptic number.

13991815 is a deficient number, since it is larger than the sum of its proper divisors (2798369).

13991815 is an equidigital number, since it uses as much as digits as its factorization.

13991815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2798368.

The product of its digits is 9720, while the sum is 37.

The square root of 13991815 is about 3740.5634602290. The cubic root of 13991815 is about 240.9672481792.

The spelling of 13991815 in words is "thirteen million, nine hundred ninety-one thousand, eight hundred fifteen".