642791689 has 2 divisors, whose sum is σ = 642791690. Its totient is φ = 642791688.

The previous prime is 642791687. The next prime is 642791701. The reversal of 642791689 is 986197246.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 435431689 + 207360000 = 20867^2 + 14400^2 .

It is a cyclic number.

It is not a de Polignac number, because 642791689 - 2¹ = 642791687 is a prime.

It is a super-3 number, since 3×642791689³ (a number of 27 digits) contains 333 as substring.

Together with 642791687, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (642791683) 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 as a sum of consecutive naturals, namely, 321395844 + 321395845.

It is an arithmetic number, because the mean of its divisors is an integer number (321395845).

Almost surely, 2^642791689 is an apocalyptic number.

It is an amenable number.

642791689 is a deficient number, since it is larger than the sum of its proper divisors (1).

642791689 is an equidigital number, since it uses as much as digits as its factorization.

642791689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1306368, while the sum is 52.

The square root of 642791689 is about 25353.3368415284. The cubic root of 642791689 is about 863.0250817686.

The spelling of 642791689 in words is "six hundred forty-two million, seven hundred ninety-one thousand, six hundred eighty-nine".