640430729 has 2 divisors, whose sum is σ = 640430730. Its totient is φ = 640430728.

The previous prime is 640430717. The next prime is 640430731. The reversal of 640430729 is 927034046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 413024329 + 227406400 = 20323^2 + 15080^2 .

It is a cyclic number.

It is not a de Polignac number, because 640430729 - 2²⁰ = 639382153 is a prime.

Together with 640430731, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (640430779) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320215364 + 320215365.

It is an arithmetic number, because the mean of its divisors is an integer number (320215365).

Almost surely, 2^640430729 is an apocalyptic number.

It is an amenable number.

640430729 is a deficient number, since it is larger than the sum of its proper divisors (1).

640430729 is an equidigital number, since it uses as much as digits as its factorization.

640430729 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36288, while the sum is 35.

The square root of 640430729 is about 25306.7328788210. The cubic root of 640430729 is about 861.9671613037.

The spelling of 640430729 in words is "six hundred forty million, four hundred thirty thousand, seven hundred twenty-nine".