1391808221 has 4 divisors (see below), whose sum is σ = 1391882844. Its totient is φ = 1391733600.

The previous prime is 1391808217. The next prime is 1391808233. The reversal of 1391808221 is 1228081931.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 634788025 + 757020196 = 25195^2 + 27514^2 .

It is a cyclic number.

It is not a de Polignac number, because 1391808221 - 2² = 1391808217 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1391808211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17831 + ... + 55691.

It is an arithmetic number, because the mean of its divisors is an integer number (347970711).

Almost surely, 2^1391808221 is an apocalyptic number.

It is an amenable number.

1391808221 is a deficient number, since it is larger than the sum of its proper divisors (74623).

1391808221 is an equidigital number, since it uses as much as digits as its factorization.

1391808221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74622.

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 1391808221 is about 37306.9460154540. The cubic root of 1391808221 is about 1116.5027552487.

The spelling of 1391808221 in words is "one billion, three hundred ninety-one million, eight hundred eight thousand, two hundred twenty-one".