638700206509 has 4 divisors (see below), whose sum is σ = 638908866940. Its totient is φ = 638491546080.

The previous prime is 638700206503. The next prime is 638700206581. The reversal of 638700206509 is 905602007836.

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

It can be written as a sum of positive squares in 2 ways, for example, as 625926234025 + 12773972484 = 791155^2 + 113022^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638700206509 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 (638700206503) 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, 104325624 + ... + 104331745.

It is an arithmetic number, because the mean of its divisors is an integer number (159727216735).

Almost surely, 2^638700206509 is an apocalyptic number.

It is an amenable number.

638700206509 is a deficient number, since it is larger than the sum of its proper divisors (208660431).

638700206509 is a wasteful number, since it uses less digits than its factorization.

638700206509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208660430.

The product of its (nonzero) digits is 544320, while the sum is 46.

The spelling of 638700206509 in words is "six hundred thirty-eight billion, seven hundred million, two hundred six thousand, five hundred nine".