646861 has 4 divisors (see below), whose sum is σ = 660672. Its totient is φ = 633052.

The previous prime is 646859. The next prime is 646873. The reversal of 646861 is 168646.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 646861 - 2¹ = 646859 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 (646831) 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, 6835 + ... + 6928.

It is an arithmetic number, because the mean of its divisors is an integer number (165168).

2⁶⁴⁶⁸⁶¹ is an apocalyptic number.

It is an amenable number.

646861 is a deficient number, since it is larger than the sum of its proper divisors (13811).

646861 is a wasteful number, since it uses less digits than its factorization.

646861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13810.

The product of its digits is 6912, while the sum is 31.

The square root of 646861 is about 804.2766936820. The cubic root of 646861 is about 86.4842431789.

The spelling of 646861 in words is "six hundred forty-six thousand, eight hundred sixty-one".