640409730109 has 2 divisors, whose sum is σ = 640409730110. Its totient is φ = 640409730108.

The previous prime is 640409730019. The next prime is 640409730137. The reversal of 640409730109 is 901037904046.

Together with previous prime (640409730019) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 364065010884 + 276344719225 = 603378^2 + 525685^2 .

It is a cyclic number.

It is not a de Polignac number, because 640409730109 - 2¹¹ = 640409728061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640409730139) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320204865054 + 320204865055.

It is an arithmetic number, because the mean of its divisors is an integer number (320204865055).

Almost surely, 2^640409730109 is an apocalyptic number.

It is an amenable number.

640409730109 is a deficient number, since it is larger than the sum of its proper divisors (1).

640409730109 is an equidigital number, since it uses as much as digits as its factorization.

640409730109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 163296, while the sum is 43.

The spelling of 640409730109 in words is "six hundred forty billion, four hundred nine million, seven hundred thirty thousand, one hundred nine".