643541 has 4 divisors (see below), whose sum is σ = 660972. Its totient is φ = 626112.

The previous prime is 643523. The next prime is 643547. The reversal of 643541 is 145346.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 145346 = 2 ⋅72673.

It can be written as a sum of positive squares in 2 ways, for example, as 372100 + 271441 = 610^2 + 521^2 .

It is a cyclic number.

It is not a de Polignac number, because 643541 - 2¹⁰ = 642517 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 (643547) 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, 8660 + ... + 8733.

It is an arithmetic number, because the mean of its divisors is an integer number (165243).

2⁶⁴³⁵⁴¹ is an apocalyptic number.

It is an amenable number.

643541 is a deficient number, since it is larger than the sum of its proper divisors (17431).

643541 is a wasteful number, since it uses less digits than its factorization.

643541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17430.

The product of its digits is 1440, while the sum is 23.

The square root of 643541 is about 802.2100722379. The cubic root of 643541 is about 86.3360298232.

Adding to 643541 its reverse (145346), we get a palindrome (788887).

The spelling of 643541 in words is "six hundred forty-three thousand, five hundred forty-one".