21121818221 has 8 divisors (see below), whose sum is σ = 24548360640. Its totient is φ = 17797560768.

The previous prime is 21121818199. The next prime is 21121818227. The reversal of 21121818221 is 12281812112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21121818221 - 2¹⁸ = 21121556077 is a prime.

It is a super-2 number, since 2×21121818221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121818227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25570796 + ... + 25571621.

It is an arithmetic number, because the mean of its divisors is an integer number (3068545080).

Almost surely, 2^21121818221 is an apocalyptic number.

It is an amenable number.

21121818221 is a deficient number, since it is larger than the sum of its proper divisors (3426542419).

21121818221 is an equidigital number, since it uses as much as digits as its factorization.

21121818221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51142483.

The product of its digits is 1024, while the sum is 29.

The spelling of 21121818221 in words is "twenty-one billion, one hundred twenty-one million, eight hundred eighteen thousand, two hundred twenty-one".