642865 has 16 divisors (see below), whose sum is σ = 832320. Its totient is φ = 475200.

The previous prime is 642853. The next prime is 642869. The reversal of 642865 is 568246.

642865 = 11² + 12² + ... + 124².

It is not a de Polignac number, because 642865 - 2⁵ = 642833 is a prime.

Its product of digits (11520) is a multiple of the sum of its prime divisors (192).

It is not an unprimeable number, because it can be changed into a prime (642869) 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 15 ways as a sum of consecutive naturals, for example, 6315 + ... + 6415.

It is an arithmetic number, because the mean of its divisors is an integer number (52020).

2⁶⁴²⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

642865 is a deficient number, since it is larger than the sum of its proper divisors (189455).

642865 is a wasteful number, since it uses less digits than its factorization.

642865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 192.

The product of its digits is 11520, while the sum is 31.

The square root of 642865 is about 801.7886255117. The cubic root of 642865 is about 86.3057890130.

The spelling of 642865 in words is "six hundred forty-two thousand, eight hundred sixty-five".