21212220012121 has 8 divisors (see below), whose sum is σ = 21281214710600. Its totient is φ = 21143261115648.

The previous prime is 21212220012101. The next prime is 21212220012157. The reversal of 21212220012121 is 12121002221212.

It can be written as a sum of positive squares in 4 ways, for example, as 12604239560025 + 8607980452096 = 3550245^2 + 2933936^2 .

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 21212220012121 - 2³⁵ = 21177860273753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21212220012101) 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, 7763346 + ... + 10133803.

It is an arithmetic number, because the mean of its divisors is an integer number (2660151838825).

Almost surely, 2^{21212220012121} is an apocalyptic number.

It is an amenable number.

21212220012121 is a deficient number, since it is larger than the sum of its proper divisors (68994698479).

21212220012121 is a wasteful number, since it uses less digits than its factorization.

21212220012121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17901003.

The product of its (nonzero) digits is 128, while the sum is 19.

Adding to 21212220012121 its reverse (12121002221212), we get a palindrome (33333222233333).

The spelling of 21212220012121 in words is "twenty-one trillion, two hundred twelve billion, two hundred twenty million, twelve thousand, one hundred twenty-one".