21163871 has 4 divisors (see below), whose sum is σ = 21230952. Its totient is φ = 21096792.

The previous prime is 21163867. The next prime is 21163927. The reversal of 21163871 is 17836112.

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 21163871 - 2² = 21163867 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21163171) 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, 33065 + ... + 33698.

It is an arithmetic number, because the mean of its divisors is an integer number (5307738).

Almost surely, 2^21163871 is an apocalyptic number.

21163871 is a deficient number, since it is larger than the sum of its proper divisors (67081).

21163871 is an equidigital number, since it uses as much as digits as its factorization.

21163871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67080.

The product of its digits is 2016, while the sum is 29.

The square root of 21163871 is about 4600.4207416279. The cubic root of 21163871 is about 276.6081902509.

Adding to 21163871 its reverse (17836112), we get a palindrome (38999983).

The spelling of 21163871 in words is "twenty-one million, one hundred sixty-three thousand, eight hundred seventy-one".