21111212002121 has 8 divisors (see below), whose sum is σ = 21509835792840. Its totient is φ = 20712599286912.

The previous prime is 21111212002099. The next prime is 21111212002151. The reversal of 21111212002121 is 12120021211112.

It can be written as a sum of positive squares in 4 ways, for example, as 3564864967225 + 17546347034896 = 1888085^2 + 4188836^2 .

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 21111212002121 - 2¹⁸ = 21111211739977 is a prime.

It is a super-2 number, since 2×21111212002121² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21111212002121.

It is not an unprimeable number, because it can be changed into a prime (21111212002151) 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, 1130711 + ... + 6595523.

It is an arithmetic number, because the mean of its divisors is an integer number (2688729474105).

Almost surely, 2^{21111212002121} is an apocalyptic number.

It is an amenable number.

21111212002121 is a deficient number, since it is larger than the sum of its proper divisors (398623790719).

21111212002121 is an equidigital number, since it uses as much as digits as its factorization.

21111212002121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5537755.

The product of its (nonzero) digits is 32, while the sum is 17.

Adding to 21111212002121 its reverse (12120021211112), we get a palindrome (33231233213233).

The spelling of 21111212002121 in words is "twenty-one trillion, one hundred eleven billion, two hundred twelve million, two thousand, one hundred twenty-one".