21120206871 has 4 divisors (see below), whose sum is σ = 28160275832. Its totient is φ = 14080137912.

The previous prime is 21120206867. The next prime is 21120206983. The reversal of 21120206871 is 17860202112.

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

It is not a de Polignac number, because 21120206871 - 2² = 21120206867 is a prime.

It is a super-2 number, since 2×21120206871² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120206851) 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, 3520034476 + ... + 3520034481.

It is an arithmetic number, because the mean of its divisors is an integer number (7040068958).

Almost surely, 2^21120206871 is an apocalyptic number.

21120206871 is a deficient number, since it is larger than the sum of its proper divisors (7040068961).

21120206871 is an equidigital number, since it uses as much as digits as its factorization.

21120206871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7040068960.

The product of its (nonzero) digits is 2688, while the sum is 30.

Adding to 21120206871 its reverse (17860202112), we get a palindrome (38980408983).

The spelling of 21120206871 in words is "twenty-one billion, one hundred twenty million, two hundred six thousand, eight hundred seventy-one".