21210111231 has 16 divisors (see below), whose sum is σ = 28684320768. Its totient is φ = 13938069600.

The previous prime is 21210111229. The next prime is 21210111239. The reversal of 21210111231 is 13211101212.

It is not a de Polignac number, because 21210111231 - 2¹ = 21210111229 is a prime.

It is a super-2 number, since 2×21210111231² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21210111231.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210111239) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1738605 + ... + 1750761.

It is an arithmetic number, because the mean of its divisors is an integer number (1792770048).

Almost surely, 2^21210111231 is an apocalyptic number.

21210111231 is a deficient number, since it is larger than the sum of its proper divisors (7474209537).

21210111231 is a wasteful number, since it uses less digits than its factorization.

21210111231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20422.

The product of its (nonzero) digits is 24, while the sum is 15.

Adding to 21210111231 its reverse (13211101212), we get a palindrome (34421212443).

The spelling of 21210111231 in words is "twenty-one billion, two hundred ten million, one hundred eleven thousand, two hundred thirty-one".