643855 has 8 divisors (see below), whose sum is σ = 785664. Its totient is φ = 506400.

The previous prime is 643849. The next prime is 643859. The reversal of 643855 is 558346.

643855 = T₁₉₂ + T₁₉₃ + ... + T₂₂₁.

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

It is not a de Polignac number, because 643855 - 2³ = 643847 is a prime.

It is a super-2 number, since 2×643855² = 829098522050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643859) 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 7 ways as a sum of consecutive naturals, for example, 751 + ... + 1360.

It is an arithmetic number, because the mean of its divisors is an integer number (98208).

2⁶⁴³⁸⁵⁵ is an apocalyptic number.

643855 is a deficient number, since it is larger than the sum of its proper divisors (141809).

643855 is a wasteful number, since it uses less digits than its factorization.

643855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2177.

The product of its digits is 14400, while the sum is 31.

The square root of 643855 is about 802.4057577062. The cubic root of 643855 is about 86.3500693874.

The spelling of 643855 in words is "six hundred forty-three thousand, eight hundred fifty-five".