640428239 has 4 divisors (see below), whose sum is σ = 698649000. Its totient is φ = 582207480.

The previous prime is 640428223. The next prime is 640428259. The reversal of 640428239 is 932824046.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 640428239 - 2⁴ = 640428223 is a prime.

It is a super-2 number, since 2×640428239² = 820296658617282242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640428259) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29110364 + ... + 29110385.

It is an arithmetic number, because the mean of its divisors is an integer number (174662250).

Almost surely, 2^640428239 is an apocalyptic number.

640428239 is a deficient number, since it is larger than the sum of its proper divisors (58220761).

640428239 is a wasteful number, since it uses less digits than its factorization.

640428239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58220760.

The product of its (nonzero) digits is 82944, while the sum is 38.

The square root of 640428239 is about 25306.6836823792. The cubic root of 640428239 is about 861.9660441905.

It can be divided in two parts, 6404 and 28239, that added together give a palindrome (34643).

The spelling of 640428239 in words is "six hundred forty million, four hundred twenty-eight thousand, two hundred thirty-nine".