21112121309 has 4 divisors (see below), whose sum is σ = 21115327200. Its totient is φ = 21108915420.

The previous prime is 21112121269. The next prime is 21112121351. The reversal of 21112121309 is 90312121112.

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 a de Polignac number, because none of the positive numbers 2^k-21112121309 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21112121369) 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, 1593047 + ... + 1606244.

It is an arithmetic number, because the mean of its divisors is an integer number (5278831800).

Almost surely, 2^21112121309 is an apocalyptic number.

It is an amenable number.

21112121309 is a deficient number, since it is larger than the sum of its proper divisors (3205891).

21112121309 is an equidigital number, since it uses as much as digits as its factorization.

21112121309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3205890.

The product of its (nonzero) digits is 216, while the sum is 23.

The spelling of 21112121309 in words is "twenty-one billion, one hundred twelve million, one hundred twenty-one thousand, three hundred nine".