21100211212121 has 4 divisors (see below), whose sum is σ = 21105900137700. Its totient is φ = 21094522286544.

The previous prime is 21100211212103. The next prime is 21100211212169. The reversal of 21100211212121 is 12121211200112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8844610572121 + 12255600640000 = 2973989^2 + 3500800^2 .

It is a cyclic number.

It is not a de Polignac number, because 21100211212121 - 2²⁶ = 21100144103257 is a prime.

It is a super-2 number, since 2×21100211212121² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21100211212121.

It is not an unprimeable number, because it can be changed into a prime (21100211212021) 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, 2844457226 + ... + 2844464643.

It is an arithmetic number, because the mean of its divisors is an integer number (5276475034425).

Almost surely, 2^{21100211212121} is an apocalyptic number.

It is an amenable number.

21100211212121 is a deficient number, since it is larger than the sum of its proper divisors (5688925579).

21100211212121 is an equidigital number, since it uses as much as digits as its factorization.

21100211212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5688925578.

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

Adding to 21100211212121 its reverse (12121211200112), we get a palindrome (33221422412233).

The spelling of 21100211212121 in words is "twenty-one trillion, one hundred billion, two hundred eleven million, two hundred twelve thousand, one hundred twenty-one".