647391 has 4 divisors (see below), whose sum is σ = 863192. Its totient is φ = 431592.

The previous prime is 647371. The next prime is 647399. The reversal of 647391 is 193746.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 647391 - 2⁵ = 647359 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 647391.

It is not an unprimeable number, because it can be changed into a prime (647399) 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, 107896 + ... + 107901.

It is an arithmetic number, because the mean of its divisors is an integer number (215798).

2⁶⁴⁷³⁹¹ is an apocalyptic number.

647391 is a deficient number, since it is larger than the sum of its proper divisors (215801).

647391 is a wasteful number, since it uses less digits than its factorization.

647391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215800.

The product of its digits is 4536, while the sum is 30.

The square root of 647391 is about 804.6061148164. The cubic root of 647391 is about 86.5078567713.

The spelling of 647391 in words is "six hundred forty-seven thousand, three hundred ninety-one".