3985815221 has 4 divisors (see below), whose sum is σ = 3986004492. Its totient is φ = 3985625952.

The previous prime is 3985815209. The next prime is 3985815227. The reversal of 3985815221 is 1225185893.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1225185893 = 139 ⋅8814287.

It can be written as a sum of positive squares in 2 ways, for example, as 1314062500 + 2671752721 = 36250^2 + 51689^2 .

It is a cyclic number.

It is not a de Polignac number, because 3985815221 - 2¹⁰ = 3985814197 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 (3985815227) 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 3 ways as a sum of consecutive naturals, for example, 58430 + ... + 106703.

It is an arithmetic number, because the mean of its divisors is an integer number (996501123).

Almost surely, 2^3985815221 is an apocalyptic number.

It is an amenable number.

3985815221 is a deficient number, since it is larger than the sum of its proper divisors (189271).

3985815221 is a wasteful number, since it uses less digits than its factorization.

3985815221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189270.

The product of its digits is 172800, while the sum is 44.

The square root of 3985815221 is about 63133.3130842981. The cubic root of 3985815221 is about 1585.5224184561.

The spelling of 3985815221 in words is "three billion, nine hundred eighty-five million, eight hundred fifteen thousand, two hundred twenty-one".