21211220231 has 4 divisors (see below), whose sum is σ = 21417154512. Its totient is φ = 21005285952.

The previous prime is 21211220227. The next prime is 21211220237. The reversal of 21211220231 is 13202211212.

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 21211220231 - 2² = 21211220227 is a prime.

It is a super-2 number, since 2×21211220231² (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 (21211220237) 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, 102966986 + ... + 102967191.

It is an arithmetic number, because the mean of its divisors is an integer number (5354288628).

Almost surely, 2^21211220231 is an apocalyptic number.

21211220231 is a deficient number, since it is larger than the sum of its proper divisors (205934281).

21211220231 is a wasteful number, since it uses less digits than its factorization.

21211220231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 205934280.

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

Adding to 21211220231 its reverse (13202211212), we get a palindrome (34413431443).

The spelling of 21211220231 in words is "twenty-one billion, two hundred eleven million, two hundred twenty thousand, two hundred thirty-one".