643557 has 4 divisors (see below), whose sum is σ = 858080. Its totient is φ = 429036.

The previous prime is 643553. The next prime is 643567. The reversal of 643557 is 755346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 643557 - 2² = 643553 is a prime.

It is a super-2 number, since 2×643557² = 828331224498, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

643557 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643557.

It is not an unprimeable number, because it can be changed into a prime (643553) 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, 107257 + ... + 107262.

It is an arithmetic number, because the mean of its divisors is an integer number (214520).

2⁶⁴³⁵⁵⁷ is an apocalyptic number.

It is an amenable number.

643557 is a deficient number, since it is larger than the sum of its proper divisors (214523).

643557 is a wasteful number, since it uses less digits than its factorization.

643557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214522.

The product of its digits is 12600, while the sum is 30.

The square root of 643557 is about 802.2200446262. The cubic root of 643557 is about 86.3367453254.

The spelling of 643557 in words is "six hundred forty-three thousand, five hundred fifty-seven".