640423549 has 2 divisors, whose sum is σ = 640423550. Its totient is φ = 640423548.

The previous prime is 640423429. The next prime is 640423579. The reversal of 640423549 is 945324046.

It is a happy number.

640423549 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 551404324 + 89019225 = 23482^2 + 9435^2 .

It is a cyclic number.

It is not a de Polignac number, because 640423549 - 2¹³ = 640415357 is a prime.

It is a super-2 number, since 2×640423549² = 820284644227510802, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640423579) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320211774 + 320211775.

It is an arithmetic number, because the mean of its divisors is an integer number (320211775).

Almost surely, 2^640423549 is an apocalyptic number.

It is an amenable number.

640423549 is a deficient number, since it is larger than the sum of its proper divisors (1).

640423549 is an equidigital number, since it uses as much as digits as its factorization.

640423549 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 103680, while the sum is 37.

The square root of 640423549 is about 25306.5910189421. The cubic root of 640423549 is about 861.9639400616.

The spelling of 640423549 in words is "six hundred forty million, four hundred twenty-three thousand, five hundred forty-nine".