13821391 has 4 divisors (see below), whose sum is σ = 14634432. Its totient is φ = 13008352.

The previous prime is 13821383. The next prime is 13821407. The reversal of 13821391 is 19312831.

13821391 = T₃₀₃₄ + T₃₀₃₅ + T₃₀₃₆.

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 13821391 - 2³ = 13821383 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 (13825391) 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, 406495 + ... + 406528.

It is an arithmetic number, because the mean of its divisors is an integer number (3658608).

Almost surely, 2^13821391 is an apocalyptic number.

13821391 is the 3036-th centered triangular number.

13821391 is a deficient number, since it is larger than the sum of its proper divisors (813041).

13821391 is an equidigital number, since it uses as much as digits as its factorization.

13821391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 813040.

The product of its digits is 1296, while the sum is 28.

The square root of 13821391 is about 3717.7131411662. The cubic root of 13821391 is about 239.9849006704.

The spelling of 13821391 in words is "thirteen million, eight hundred twenty-one thousand, three hundred ninety-one".