21536161 has 8 divisors (see below), whose sum is σ = 22951080. Its totient is φ = 20137728.

The previous prime is 21536159. The next prime is 21536173. The reversal of 21536161 is 16163512.

It can be written as a sum of positive squares in 4 ways, for example, as 90000 + 21446161 = 300^2 + 4631^2 .

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 21536161 - 2¹ = 21536159 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21536191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1366 + ... + 6703.

It is an arithmetic number, because the mean of its divisors is an integer number (2868885).

Almost surely, 2^21536161 is an apocalyptic number.

It is an amenable number.

21536161 is a deficient number, since it is larger than the sum of its proper divisors (1414919).

21536161 is a wasteful number, since it uses less digits than its factorization.

21536161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8243.

The product of its digits is 1080, while the sum is 25.

The square root of 21536161 is about 4640.7069504549. The cubic root of 21536161 is about 278.2206941003.

Adding to 21536161 its reverse (16163512), we get a palindrome (37699673).

The spelling of 21536161 in words is "twenty-one million, five hundred thirty-six thousand, one hundred sixty-one".