21872163 has 4 divisors (see below), whose sum is σ = 29162888. Its totient is φ = 14581440.

The previous prime is 21872159. The next prime is 21872171. The reversal of 21872163 is 36127812.

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

It is not a de Polignac number, because 21872163 - 2² = 21872159 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21872163.

It is not an unprimeable number, because it can be changed into a prime (21872113) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3645358 + ... + 3645363.

It is an arithmetic number, because the mean of its divisors is an integer number (7290722).

Almost surely, 2^21872163 is an apocalyptic number.

21872163 is a deficient number, since it is larger than the sum of its proper divisors (7290725).

21872163 is an equidigital number, since it uses as much as digits as its factorization.

21872163 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7290724.

The product of its digits is 4032, while the sum is 30.

The square root of 21872163 is about 4676.7684355760. The cubic root of 21872163 is about 279.6601446337.

Adding to 21872163 its reverse (36127812), we get a palindrome (57999975).

The spelling of 21872163 in words is "twenty-one million, eight hundred seventy-two thousand, one hundred sixty-three".