638168621 has 4 divisors (see below), whose sum is σ = 638262144. Its totient is φ = 638075100.

The previous prime is 638168617. The next prime is 638168647. The reversal of 638168621 is 126861836.

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 638168621 - 2² = 638168617 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 (638168611) 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, 35645 + ... + 50466.

It is an arithmetic number, because the mean of its divisors is an integer number (159565536).

Almost surely, 2^638168621 is an apocalyptic number.

It is an amenable number.

638168621 is a deficient number, since it is larger than the sum of its proper divisors (93523).

638168621 is an equidigital number, since it uses as much as digits as its factorization.

638168621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93522.

The product of its digits is 82944, while the sum is 41.

The square root of 638168621 is about 25261.9995447708. Note that the first 3 decimals coincide. The cubic root of 638168621 is about 860.9510935308.

The spelling of 638168621 in words is "six hundred thirty-eight million, one hundred sixty-eight thousand, six hundred twenty-one".