2163531721 has 4 divisors (see below), whose sum is σ = 2329957252. Its totient is φ = 1997106192.

The previous prime is 2163531677. The next prime is 2163531739. The reversal of 2163531721 is 1271353612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 375933321 + 1787598400 = 19389^2 + 42280^2 .

It is a cyclic number.

It is not a de Polignac number, because 2163531721 - 2¹¹ = 2163529673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2163531751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83212746 + ... + 83212771.

It is an arithmetic number, because the mean of its divisors is an integer number (582489313).

Almost surely, 2^2163531721 is an apocalyptic number.

It is an amenable number.

2163531721 is a deficient number, since it is larger than the sum of its proper divisors (166425531).

2163531721 is a wasteful number, since it uses less digits than its factorization.

2163531721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 166425530.

The product of its digits is 7560, while the sum is 31.

The square root of 2163531721 is about 46513.7799044541. The cubic root of 2163531721 is about 1293.3649546699.

The spelling of 2163531721 in words is "two billion, one hundred sixty-three million, five hundred thirty-one thousand, seven hundred twenty-one".