21105271 has 4 divisors (see below), whose sum is σ = 23023944. Its totient is φ = 19186600.

The previous prime is 21105239. The next prime is 21105307. The reversal of 21105271 is 17250112.

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 21105271 - 2⁵ = 21105239 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 (21105221) 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 3 ways as a sum of consecutive naturals, for example, 959320 + ... + 959341.

It is an arithmetic number, because the mean of its divisors is an integer number (5755986).

Almost surely, 2^21105271 is an apocalyptic number.

21105271 is a deficient number, since it is larger than the sum of its proper divisors (1918673).

21105271 is a wasteful number, since it uses less digits than its factorization.

21105271 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1918672.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 21105271 is about 4594.0473441183. The cubic root of 21105271 is about 276.3526569188.

Adding to 21105271 its reverse (17250112), we get a palindrome (38355383).

It can be divided in two parts, 2110 and 5271, that added together give a triangular number (7381 = T₁₂₁).

The spelling of 21105271 in words is "twenty-one million, one hundred five thousand, two hundred seventy-one".