643995 has 24 divisors (see below), whose sum is σ = 1218672. Its totient is φ = 312000.

The previous prime is 643991. The next prime is 644009. The reversal of 643995 is 599346.

643995 is a `hidden beast` number, since 643 + 9 + 9 + 5 = 666.

It is not a de Polignac number, because 643995 - 2² = 643991 is a prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643995.

It is not an unprimeable number, because it can be changed into a prime (643991) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 156 + ... + 1145.

It is an arithmetic number, because the mean of its divisors is an integer number (50778).

2⁶⁴³⁹⁹⁵ is an apocalyptic number.

643995 is a deficient number, since it is larger than the sum of its proper divisors (574677).

643995 is a wasteful number, since it uses less digits than its factorization.

643995 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1323 (or 1320 counting only the distinct ones).

The product of its digits is 29160, while the sum is 36.

The square root of 643995 is about 802.4929906236. The cubic root of 643995 is about 86.3563275944.

The spelling of 643995 in words is "six hundred forty-three thousand, nine hundred ninety-five".