638081809 has 8 divisors (see below), whose sum is σ = 660433320. Its totient is φ = 615753600.

The previous prime is 638081789. The next prime is 638081813. The reversal of 638081809 is 908180836.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 82301184 + 555780625 = 9072^2 + 23575^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638081809 - 2¹³ = 638073617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638081819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 64429 + ... + 73669.

It is an arithmetic number, because the mean of its divisors is an integer number (82554165).

Almost surely, 2^638081809 is an apocalyptic number.

It is an amenable number.

638081809 is a deficient number, since it is larger than the sum of its proper divisors (22351511).

638081809 is a wasteful number, since it uses less digits than its factorization.

638081809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11651.

The product of its (nonzero) digits is 82944, while the sum is 43.

The square root of 638081809 is about 25260.2812533828. The cubic root of 638081809 is about 860.9120525035.

The spelling of 638081809 in words is "six hundred thirty-eight million, eighty-one thousand, eight hundred nine".