11391821 has 4 divisors (see below), whose sum is σ = 13019232. Its totient is φ = 9764412.

The previous prime is 11391817. The next prime is 11391823. The reversal of 11391821 is 12819311.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 11391821 - 2² = 11391817 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 (11391823) 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, 813695 + ... + 813708.

It is an arithmetic number, because the mean of its divisors is an integer number (3254808).

Almost surely, 2^11391821 is an apocalyptic number.

It is an amenable number.

11391821 is a deficient number, since it is larger than the sum of its proper divisors (1627411).

11391821 is an equidigital number, since it uses as much as digits as its factorization.

11391821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1627410.

The product of its digits is 432, while the sum is 26.

The square root of 11391821 is about 3375.1771805344. The cubic root of 11391821 is about 225.0078746215.

The spelling of 11391821 in words is "eleven million, three hundred ninety-one thousand, eight hundred twenty-one".