647891 has 2 divisors, whose sum is σ = 647892. Its totient is φ = 647890.

The previous prime is 647861. The next prime is 647893. The reversal of 647891 is 198746.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 647891 - 2¹⁴ = 631507 is a prime.

It is a Sophie Germain prime.

Together with 647893, it forms a pair of twin primes.

It is a Chen prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 647891.

It is not a weakly prime, because it can be changed into another prime (647893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323945 + 323946.

It is an arithmetic number, because the mean of its divisors is an integer number (323946).

2⁶⁴⁷⁸⁹¹ is an apocalyptic number.

647891 is a deficient number, since it is larger than the sum of its proper divisors (1).

647891 is an equidigital number, since it uses as much as digits as its factorization.

647891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12096, while the sum is 35.

The square root of 647891 is about 804.9167658833. The cubic root of 647891 is about 86.5301219339.

The spelling of 647891 in words is "six hundred forty-seven thousand, eight hundred ninety-one".