646447 has 4 divisors (see below), whose sum is σ = 662256. Its totient is φ = 630640.

The previous prime is 646433. The next prime is 646453. The reversal of 646447 is 744646.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646447 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646147) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7843 + ... + 7924.

It is an arithmetic number, because the mean of its divisors is an integer number (165564).

2⁶⁴⁶⁴⁴⁷ is an apocalyptic number.

646447 is a deficient number, since it is larger than the sum of its proper divisors (15809).

646447 is a wasteful number, since it uses less digits than its factorization.

646447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15808.

The product of its digits is 16128, while the sum is 31.

The square root of 646447 is about 804.0192783758. The cubic root of 646447 is about 86.4657888701.

Subtracting from 646447 its sum of digits (31), we obtain a square (646416 = 804²).

The spelling of 646447 in words is "six hundred forty-six thousand, four hundred forty-seven".