656641 has 4 divisors (see below), whose sum is σ = 661572. Its totient is φ = 651712.

The previous prime is 656609. The next prime is 656651. The reversal of 656641 is 146656.

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 484416 + 172225 = 696^2 + 415^2 .

It is a cyclic number.

It is not a de Polignac number, because 656641 - 2⁵ = 656609 is a prime.

It is a Duffinian number.

656641 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2260 + ... + 2533.

It is an arithmetic number, because the mean of its divisors is an integer number (165393).

2⁶⁵⁶⁶⁴¹ is an apocalyptic number.

656641 is the 513-rd centered pentagonal number.

It is an amenable number.

656641 is a deficient number, since it is larger than the sum of its proper divisors (4931).

656641 is a wasteful number, since it uses less digits than its factorization.

656641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4930.

The product of its digits is 4320, while the sum is 28.

The square root of 656641 is about 810.3338818043. Note that the first 3 decimals coincide. The cubic root of 656641 is about 86.9179214438.

The spelling of 656641 in words is "six hundred fifty-six thousand, six hundred forty-one".