21661163 has 4 divisors (see below), whose sum is σ = 21674520. Its totient is φ = 21647808.

The previous prime is 21661151. The next prime is 21661181. The reversal of 21661163 is 36116612.

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

It is a cyclic number.

It is not a de Polignac number, because 21661163 - 2¹² = 21657067 is a prime.

It is a super-3 number, since 3×21661163³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21661183) 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, 3845 + ... + 7622.

It is an arithmetic number, because the mean of its divisors is an integer number (5418630).

Almost surely, 2^21661163 is an apocalyptic number.

21661163 is a deficient number, since it is larger than the sum of its proper divisors (13357).

21661163 is a wasteful number, since it uses less digits than its factorization.

21661163 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13356.

The product of its digits is 1296, while the sum is 26.

The square root of 21661163 is about 4654.1554550745. The cubic root of 21661163 is about 278.7579466455.

Adding to 21661163 its reverse (36116612), we get a palindrome (57777775).

The spelling of 21661163 in words is "twenty-one million, six hundred sixty-one thousand, one hundred sixty-three".