639500121 has 12 divisors (see below), whose sum is σ = 994778148. Its totient is φ = 393538464.

The previous prime is 639500111. The next prime is 639500123. The reversal of 639500121 is 121005936.

639500121 is a `hidden beast` number, since 6 + 39 + 500 + 121 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 244484496 + 395015625 = 15636^2 + 19875^2 .

It is not a de Polignac number, because 639500121 - 2¹¹ = 639498073 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639500123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2732790 + ... + 2733023.

It is an arithmetic number, because the mean of its divisors is an integer number (82898179).

Almost surely, 2^639500121 is an apocalyptic number.

It is an amenable number.

639500121 is a deficient number, since it is larger than the sum of its proper divisors (355278027).

639500121 is a wasteful number, since it uses less digits than its factorization.

639500121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5465832 (or 5465829 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 639500121 is about 25288.3396252107. The cubic root of 639500121 is about 861.5494516024.

The spelling of 639500121 in words is "six hundred thirty-nine million, five hundred thousand, one hundred twenty-one".