2001638521 has 8 divisors (see below), whose sum is σ = 2009442024. Its totient is φ = 1993850880.

The previous prime is 2001638501. The next prime is 2001638579. The reversal of 2001638521 is 1258361002.

It can be written as a sum of positive squares in 4 ways, for example, as 674129296 + 1327509225 = 25964^2 + 36435^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2001638521 - 2⁷ = 2001638393 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 2001638521.

It is not an unprimeable number, because it can be changed into a prime (2001638501) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 289521 + ... + 296353.

It is an arithmetic number, because the mean of its divisors is an integer number (251180253).

Almost surely, 2^2001638521 is an apocalyptic number.

It is an amenable number.

2001638521 is a deficient number, since it is larger than the sum of its proper divisors (7803503).

2001638521 is an equidigital number, since it uses as much as digits as its factorization.

2001638521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7931.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 2001638521 is about 44739.6750211711. The cubic root of 2001638521 is about 1260.2650238270.

Adding to 2001638521 its reverse (1258361002), we get a palindrome (3259999523).

The spelling of 2001638521 in words is "two billion, one million, six hundred thirty-eight thousand, five hundred twenty-one".