999643 has 4 divisors (see below), whose sum is σ = 1020960. Its totient is φ = 978328.

The previous prime is 999631. The next prime is 999653. The reversal of 999643 is 346999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 346999 = 353 ⋅983.

It is a cyclic number.

It is not a de Polignac number, because 999643 - 2⁵ = 999611 is a prime.

It is a super-2 number, since 2×999643² = 1998572254898, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 999596 and 999605.

It is not an unprimeable number, because it can be changed into a prime (999613) 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, 10588 + ... + 10681.

It is an arithmetic number, because the mean of its divisors is an integer number (255240).

2⁹⁹⁹⁶⁴³ is an apocalyptic number.

999643 is a deficient number, since it is larger than the sum of its proper divisors (21317).

999643 is a wasteful number, since it uses less digits than its factorization.

999643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21316.

The product of its digits is 52488, while the sum is 40.

The square root of 999643 is about 999.8214840660. The cubic root of 999643 is about 99.9880985836.

The spelling of 999643 in words is "nine hundred ninety-nine thousand, six hundred forty-three".