642871 has 2 divisors, whose sum is σ = 642872. Its totient is φ = 642870.

The previous prime is 642869. The next prime is 642877. The reversal of 642871 is 178246.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 642871 - 2¹ = 642869 is a prime.

Together with 642869, it forms a pair of twin primes.

It is a nialpdrome in base 15.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642877) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321435 + 321436.

It is an arithmetic number, because the mean of its divisors is an integer number (321436).

2⁶⁴²⁸⁷¹ is an apocalyptic number.

642871 is a deficient number, since it is larger than the sum of its proper divisors (1).

642871 is an equidigital number, since it uses as much as digits as its factorization.

642871 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 28.

The square root of 642871 is about 801.7923671375. The cubic root of 642871 is about 86.3060575158.

The spelling of 642871 in words is "six hundred forty-two thousand, eight hundred seventy-one".