391228109 has 4 divisors (see below), whose sum is σ = 400770300. Its totient is φ = 381685920.

The previous prime is 391228087. The next prime is 391228127. The reversal of 391228109 is 901822193.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 901822193 = 29 ⋅31097317.

It can be written as a sum of positive squares in 2 ways, for example, as 65966884 + 325261225 = 8122^2 + 18035^2 .

It is a cyclic number.

It is not a de Polignac number, because 391228109 - 2⁸ = 391227853 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 (391228129) 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, 4771034 + ... + 4771115.

It is an arithmetic number, because the mean of its divisors is an integer number (100192575).

Almost surely, 2^391228109 is an apocalyptic number.

It is an amenable number.

391228109 is a deficient number, since it is larger than the sum of its proper divisors (9542191).

391228109 is an equidigital number, since it uses as much as digits as its factorization.

391228109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9542190.

The product of its (nonzero) digits is 7776, while the sum is 35.

The square root of 391228109 is about 19779.4870762616. The cubic root of 391228109 is about 731.3804547346.

The spelling of 391228109 in words is "three hundred ninety-one million, two hundred twenty-eight thousand, one hundred nine".