642842209 has 2 divisors, whose sum is σ = 642842210. Its totient is φ = 642842208.

The previous prime is 642842191. The next prime is 642842251. The reversal of 642842209 is 902248246.

642842209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 642774609 + 67600 = 25353^2 + 260^2 .

It is a cyclic number.

It is not a de Polignac number, because 642842209 - 2⁵ = 642842177 is a prime.

It is a super-2 number, since 2×642842209² = 826492211343999362, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (642842269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321421104 + 321421105.

It is an arithmetic number, because the mean of its divisors is an integer number (321421105).

Almost surely, 2^642842209 is an apocalyptic number.

It is an amenable number.

642842209 is a deficient number, since it is larger than the sum of its proper divisors (1).

642842209 is an equidigital number, since it uses as much as digits as its factorization.

642842209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 55296, while the sum is 37.

The square root of 642842209 is about 25354.3331405107. Note that the first 3 decimals coincide. The cubic root of 642842209 is about 863.0476908999.

The spelling of 642842209 in words is "six hundred forty-two million, eight hundred forty-two thousand, two hundred nine".