638564081 has 4 divisors (see below), whose sum is σ = 676126692. Its totient is φ = 601001472.

The previous prime is 638564041. The next prime is 638564099. The reversal of 638564081 is 180465836.

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 330912481 + 307651600 = 18191^2 + 17540^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638564081 is a prime.

It is a super-2 number, since 2×638564081² = 815528171086749122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (638564011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18781280 + ... + 18781313.

It is an arithmetic number, because the mean of its divisors is an integer number (169031673).

Almost surely, 2^638564081 is an apocalyptic number.

It is an amenable number.

638564081 is a deficient number, since it is larger than the sum of its proper divisors (37562611).

638564081 is a wasteful number, since it uses less digits than its factorization.

638564081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37562610.

The product of its (nonzero) digits is 138240, while the sum is 41.

The square root of 638564081 is about 25269.8255039484. The cubic root of 638564081 is about 861.1288947183.

The spelling of 638564081 in words is "six hundred thirty-eight million, five hundred sixty-four thousand, eighty-one".