642779 has 2 divisors, whose sum is σ = 642780. Its totient is φ = 642778.

The previous prime is 642769. The next prime is 642791. The reversal of 642779 is 977246.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642779 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (642739) 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, 321389 + 321390.

It is an arithmetic number, because the mean of its divisors is an integer number (321390).

2⁶⁴²⁷⁷⁹ is an apocalyptic number.

642779 is a deficient number, since it is larger than the sum of its proper divisors (1).

642779 is an equidigital number, since it uses as much as digits as its factorization.

642779 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21168, while the sum is 35.

The square root of 642779 is about 801.7349936232. The cubic root of 642779 is about 86.3019402896.

The spelling of 642779 in words is "six hundred forty-two thousand, seven hundred seventy-nine".