21420031211 has 4 divisors (see below), whose sum is σ = 21437633112. Its totient is φ = 21402429312.

The previous prime is 21420031183. The next prime is 21420031247. The reversal of 21420031211 is 11213002412.

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 21420031211 - 2¹⁸ = 21419769067 is a prime.

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 21420031211.

It is not an unprimeable number, because it can be changed into a prime (21420031291) 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, 8799125 + ... + 8801558.

It is an arithmetic number, because the mean of its divisors is an integer number (5359408278).

Almost surely, 2^21420031211 is an apocalyptic number.

21420031211 is a deficient number, since it is larger than the sum of its proper divisors (17601901).

21420031211 is a wasteful number, since it uses less digits than its factorization.

21420031211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17601900.

The product of its (nonzero) digits is 96, while the sum is 17.

Adding to 21420031211 its reverse (11213002412), we get a palindrome (32633033623).

The spelling of 21420031211 in words is "twenty-one billion, four hundred twenty million, thirty-one thousand, two hundred eleven".