639786437 has 6 divisors (see below), whose sum is σ = 641288754. Its totient is φ = 638287520.

The previous prime is 639786391. The next prime is 639786529. The reversal of 639786437 is 734687936.

It is a Cunningham number, because it is equal to 25294²+1.

It can be written as a sum of positive squares in 3 ways, for example, as 1 + 639786436 = 1^2 + 25294^2 .

It is not a de Polignac number, because 639786437 - 2²⁰ = 638737861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639786937) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 270263 + ... + 272619.

It is an arithmetic number, because the mean of its divisors is an integer number (106881459).

Almost surely, 2^639786437 is an apocalyptic number.

It is an amenable number.

639786437 is a deficient number, since it is larger than the sum of its proper divisors (1502317).

639786437 is an frugal number, since it uses more digits than its factorization.

639786437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3399 (or 2878 counting only the distinct ones).

The product of its digits is 4572288, while the sum is 53.

The square root of 639786437 is about 25294.0000197675. Note that the first 4 decimals coincide. The cubic root of 639786437 is about 861.6780096121.

The spelling of 639786437 in words is "six hundred thirty-nine million, seven hundred eighty-six thousand, four hundred thirty-seven".