21012871 has 4 divisors (see below), whose sum is σ = 22923144. Its totient is φ = 19102600.

The previous prime is 21012851. The next prime is 21012877. The reversal of 21012871 is 17821012.

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

It is not a de Polignac number, because 21012871 - 2⁷ = 21012743 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012877) 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, 955120 + ... + 955141.

It is an arithmetic number, because the mean of its divisors is an integer number (5730786).

Almost surely, 2^21012871 is an apocalyptic number.

21012871 is a deficient number, since it is larger than the sum of its proper divisors (1910273).

21012871 is a wasteful number, since it uses less digits than its factorization.

21012871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1910272.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21012871 is about 4583.9798210725. The cubic root of 21012871 is about 275.9487713854.

Adding to 21012871 its reverse (17821012), we get a palindrome (38833883).

The spelling of 21012871 in words is "twenty-one million, twelve thousand, eight hundred seventy-one".