13891991 has 4 divisors (see below), whose sum is σ = 13962000. Its totient is φ = 13821984.

The previous prime is 13891987. The next prime is 13891993. The reversal of 13891991 is 19919831.

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: 19919831 = 71 ⋅280561.

It is a cyclic number.

It is not a de Polignac number, because 13891991 - 2² = 13891987 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 (13891993) 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, 34706 + ... + 35103.

It is an arithmetic number, because the mean of its divisors is an integer number (3490500).

Almost surely, 2^13891991 is an apocalyptic number.

13891991 is a deficient number, since it is larger than the sum of its proper divisors (70009).

13891991 is an equidigital number, since it uses as much as digits as its factorization.

13891991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70008.

The product of its digits is 17496, while the sum is 41.

The square root of 13891991 is about 3727.1961311420. The cubic root of 13891991 is about 240.3928231260.

It can be divided in two parts, 138 and 91991, that added together give a palindrome (92129).

The spelling of 13891991 in words is "thirteen million, eight hundred ninety-one thousand, nine hundred ninety-one".