643699 has 4 divisors (see below), whose sum is σ = 735664. Its totient is φ = 551736.

The previous prime is 643697. The next prime is 643703. The reversal of 643699 is 996346.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643699 - 2¹ = 643697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643691) 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, 45972 + ... + 45985.

It is an arithmetic number, because the mean of its divisors is an integer number (183916).

2⁶⁴³⁶⁹⁹ is an apocalyptic number.

643699 is a deficient number, since it is larger than the sum of its proper divisors (91965).

643699 is an equidigital number, since it uses as much as digits as its factorization.

643699 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91964.

The product of its digits is 34992, while the sum is 37.

The square root of 643699 is about 802.3085441400. The cubic root of 643699 is about 86.3430948880.

The spelling of 643699 in words is "six hundred forty-three thousand, six hundred ninety-nine".