638288561 has 4 divisors (see below), whose sum is σ = 638376000. Its totient is φ = 638201124.

The previous prime is 638288557. The next prime is 638288587. The reversal of 638288561 is 165882836.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 638288561 - 2² = 638288557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (638288501) 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, 31661 + ... + 47738.

It is an arithmetic number, because the mean of its divisors is an integer number (159594000).

Almost surely, 2^638288561 is an apocalyptic number.

It is an amenable number.

638288561 is a deficient number, since it is larger than the sum of its proper divisors (87439).

638288561 is an equidigital number, since it uses as much as digits as its factorization.

638288561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87438.

The product of its digits is 552960, while the sum is 47.

The square root of 638288561 is about 25264.3733545877. The cubic root of 638288561 is about 861.0050270327.

The spelling of 638288561 in words is "six hundred thirty-eight million, two hundred eighty-eight thousand, five hundred sixty-one".