3828121721 has 4 divisors (see below), whose sum is σ = 3893005200. Its totient is φ = 3763238244.

The previous prime is 3828121709. The next prime is 3828121763. The reversal of 3828121721 is 1271218283.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1271218283 = 3833 ⋅331651.

It is a cyclic number.

It is not a de Polignac number, because 3828121721 - 2⁶ = 3828121657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3828121621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32441651 + ... + 32441768.

It is an arithmetic number, because the mean of its divisors is an integer number (973251300).

Almost surely, 2^3828121721 is an apocalyptic number.

It is an amenable number.

3828121721 is a deficient number, since it is larger than the sum of its proper divisors (64883479).

3828121721 is an equidigital number, since it uses as much as digits as its factorization.

3828121721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64883478.

The product of its digits is 10752, while the sum is 35.

The square root of 3828121721 is about 61871.8168554957. The cubic root of 3828121721 is about 1564.3307397736.

The spelling of 3828121721 in words is "three billion, eight hundred twenty-eight million, one hundred twenty-one thousand, seven hundred twenty-one".