640217439 has 20 divisors (see below), whose sum is σ = 957170016. Its totient is φ = 426456576.

The previous prime is 640217423. The next prime is 640217491. The reversal of 640217439 is 934712046.

640217439 is a `hidden beast` number, since 6 + 4 + 0 + 217 + 439 = 666.

It is not a de Polignac number, because 640217439 - 2⁴ = 640217423 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640217639) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 125727 + ... + 130719.

Almost surely, 2^640217439 is an apocalyptic number.

640217439 is a deficient number, since it is larger than the sum of its proper divisors (316952577).

640217439 is a wasteful number, since it uses less digits than its factorization.

640217439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6588 (or 6579 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 36.

The square root of 640217439 is about 25302.5184319664. The cubic root of 640217439 is about 861.8714604048.

The spelling of 640217439 in words is "six hundred forty million, two hundred seventeen thousand, four hundred thirty-nine".