21312222121 has 4 divisors (see below), whose sum is σ = 21465547600. Its totient is φ = 21158896644.

The previous prime is 21312222109. The next prime is 21312222131. The reversal of 21312222121 is 12122221312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21312222121 - 2¹⁷ = 21312091049 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21312222101) 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, 76662531 + ... + 76662808.

It is an arithmetic number, because the mean of its divisors is an integer number (5366386900).

Almost surely, 2^21312222121 is an apocalyptic number.

It is an amenable number.

21312222121 is a deficient number, since it is larger than the sum of its proper divisors (153325479).

21312222121 is a wasteful number, since it uses less digits than its factorization.

21312222121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153325478.

The product of its digits is 192, while the sum is 19.

Adding to 21312222121 its reverse (12122221312), we get a palindrome (33434443433).

The spelling of 21312222121 in words is "twenty-one billion, three hundred twelve million, two hundred twenty-two thousand, one hundred twenty-one".