391447891 has 2 divisors, whose sum is σ = 391447892. Its totient is φ = 391447890.

The previous prime is 391447873. The next prime is 391447897. The reversal of 391447891 is 198744193.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 391447891 - 2¹¹ = 391445843 is a prime.

It is not a weakly prime, because it can be changed into another prime (391447897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195723945 + 195723946.

It is an arithmetic number, because the mean of its divisors is an integer number (195723946).

Almost surely, 2^391447891 is an apocalyptic number.

391447891 is a deficient number, since it is larger than the sum of its proper divisors (1).

391447891 is an equidigital number, since it uses as much as digits as its factorization.

391447891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 217728, while the sum is 46.

The square root of 391447891 is about 19785.0421025582. The cubic root of 391447891 is about 731.5173860748.

The spelling of 391447891 in words is "three hundred ninety-one million, four hundred forty-seven thousand, eight hundred ninety-one".