3645521221 has 8 divisors (see below), whose sum is σ = 3704410584. Its totient is φ = 3587066880.

The previous prime is 3645521189. The next prime is 3645521227. The reversal of 3645521221 is 1221255463.

3645521221 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 1016908321 + 2628612900 = 31889^2 + 51270^2 .

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 3645521221 - 2⁵ = 3645521189 is a prime.

It is a super-2 number, since 2×3645521221² = 26579649945522661682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3645521227) 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, 91840 + ... + 125401.

It is an arithmetic number, because the mean of its divisors is an integer number (463051323).

Almost surely, 2^3645521221 is an apocalyptic number.

It is an amenable number.

3645521221 is a deficient number, since it is larger than the sum of its proper divisors (58889363).

3645521221 is a wasteful number, since it uses less digits than its factorization.

3645521221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217511.

The product of its digits is 14400, while the sum is 31.

The square root of 3645521221 is about 60378.1518514769. The cubic root of 3645521221 is about 1539.0517045105.

Adding to 3645521221 its reverse (1221255463), we get a palindrome (4866776684).

The spelling of 3645521221 in words is "three billion, six hundred forty-five million, five hundred twenty-one thousand, two hundred twenty-one".