643537 has 4 divisors (see below), whose sum is σ = 645556. Its totient is φ = 641520.

The previous prime is 643523. The next prime is 643547. The reversal of 643537 is 735346.

643537 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is the 328-th star number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 735346 = 2 ⋅367673.

It can be written as a sum of positive squares in 2 ways, for example, as 463761 + 179776 = 681^2 + 424^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643537 is a prime.

It is a Duffinian number.

643537 is a lucky number.

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

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 414 + ... + 1207.

It is an arithmetic number, because the mean of its divisors is an integer number (161389).

2⁶⁴³⁵³⁷ is an apocalyptic number.

It is an amenable number.

643537 is a deficient number, since it is larger than the sum of its proper divisors (2019).

643537 is a wasteful number, since it uses less digits than its factorization.

643537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2018.

The product of its digits is 7560, while the sum is 28.

The square root of 643537 is about 802.2075791215. The cubic root of 643537 is about 86.3358509458.

Subtracting 643537 from its reverse (735346), we obtain a square (91809 = 303²).

The spelling of 643537 in words is "six hundred forty-three thousand, five hundred thirty-seven".