646649 has 4 divisors (see below), whose sum is σ = 664164. Its totient is φ = 629136.

The previous prime is 646643. The next prime is 646669. The reversal of 646649 is 946646.

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

It can be written as a sum of positive squares in 2 ways, for example, as 310249 + 336400 = 557^2 + 580^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646643) 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, 8702 + ... + 8775.

It is an arithmetic number, because the mean of its divisors is an integer number (166041).

2⁶⁴⁶⁶⁴⁹ is an apocalyptic number.

It is an amenable number.

646649 is a deficient number, since it is larger than the sum of its proper divisors (17515).

646649 is a wasteful number, since it uses less digits than its factorization.

646649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17514.

The product of its digits is 31104, while the sum is 35.

The square root of 646649 is about 804.1448874426. The cubic root of 646649 is about 86.4747941304.

The spelling of 646649 in words is "six hundred forty-six thousand, six hundred forty-nine".