643945 has 8 divisors (see below), whose sum is σ = 799560. Its totient is φ = 497280.

The previous prime is 643927. The next prime is 643949. The reversal of 643945 is 549346.

It can be written as a sum of positive squares in 4 ways, for example, as 47961 + 595984 = 219^2 + 772^2 .

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

It is not a de Polignac number, because 643945 - 2¹¹ = 641897 is a prime.

It is a d-powerful number, because it can be written as 6⁵ + 4⁷ + 9⁶ + 3⁹ + 4⁸ + 5⁵ .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643949) 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, 2076 + ... + 2365.

It is an arithmetic number, because the mean of its divisors is an integer number (99945).

2⁶⁴³⁹⁴⁵ is an apocalyptic number.

It is an amenable number.

643945 is a deficient number, since it is larger than the sum of its proper divisors (155615).

643945 is a wasteful number, since it uses less digits than its factorization.

643945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4475.

The product of its digits is 12960, while the sum is 31.

The square root of 643945 is about 802.4618370988. The cubic root of 643945 is about 86.3540926246.

The spelling of 643945 in words is "six hundred forty-three thousand, nine hundred forty-five".