639121 has 4 divisors (see below), whose sum is σ = 730432. Its totient is φ = 547812.

The previous prime is 639091. The next prime is 639137. The reversal of 639121 is 121936.

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 639121 - 2⁷ = 638993 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639092 and 639101.

It is not an unprimeable number, because it can be changed into a prime (639151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45645 + ... + 45658.

It is an arithmetic number, because the mean of its divisors is an integer number (182608).

2⁶³⁹¹²¹ is an apocalyptic number.

It is an amenable number.

639121 is a deficient number, since it is larger than the sum of its proper divisors (91311).

639121 is an equidigital number, since it uses as much as digits as its factorization.

639121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91310.

The product of its digits is 324, while the sum is 22.

The square root of 639121 is about 799.4504362373. The cubic root of 639121 is about 86.1379164401.

The spelling of 639121 in words is "six hundred thirty-nine thousand, one hundred twenty-one".