643501 has 4 divisors (see below), whose sum is σ = 681372. Its totient is φ = 605632.

The previous prime is 643493. The next prime is 643507. The reversal of 643501 is 105346.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 105346 = 2 ⋅52673.

It can be written as a sum of positive squares in 2 ways, for example, as 189225 + 454276 = 435^2 + 674^2 .

It is a cyclic number.

It is not a de Polignac number, because 643501 - 2³ = 643493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18910 + ... + 18943.

It is an arithmetic number, because the mean of its divisors is an integer number (170343).

2⁶⁴³⁵⁰¹ is an apocalyptic number.

It is an amenable number.

643501 is a deficient number, since it is larger than the sum of its proper divisors (37871).

643501 is a wasteful number, since it uses less digits than its factorization.

643501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37870.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 643501 is about 802.1851407250. The cubic root of 643501 is about 86.3342410158.

Adding to 643501 its reverse (105346), we get a palindrome (748847).

The spelling of 643501 in words is "six hundred forty-three thousand, five hundred one".