644161 has 8 divisors (see below), whose sum is σ = 768384. Its totient is φ = 528000.

The previous prime is 644159. The next prime is 644173. The reversal of 644161 is 161446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 3-Lehmer number, since φ(644161) divides (644161-1)³.

It is a cyclic number.

It is not a de Polignac number, because 644161 - 2¹ = 644159 is a prime.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (644101) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1840 + ... + 2161.

It is an arithmetic number, because the mean of its divisors is an integer number (96048).

2⁶⁴⁴¹⁶¹ is an apocalyptic number.

It is an amenable number.

644161 is a deficient number, since it is larger than the sum of its proper divisors (124223).

644161 is a wasteful number, since it uses less digits than its factorization.

644161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4031.

The product of its digits is 576, while the sum is 22.

The square root of 644161 is about 802.5964116541. The cubic root of 644161 is about 86.3637468646.

It can be divided in two parts, 644 and 161, that multiplied together give a square (103684 = 322²).

The spelling of 644161 in words is "six hundred forty-four thousand, one hundred sixty-one".