21212020102181 has 2 divisors, whose sum is σ = 21212020102182. Its totient is φ = 21212020102180.

The previous prime is 21212020102177. The next prime is 21212020102219. The reversal of 21212020102181 is 18120102021212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20591129685025 + 620890417156 = 4537745^2 + 787966^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212020102181 - 2² = 21212020102177 is a prime.

It is a super-4 number, since 4×21212020102181⁴ (a number of 54 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21212020102151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606010051090 + 10606010051091.

It is an arithmetic number, because the mean of its divisors is an integer number (10606010051091).

Almost surely, 2^{21212020102181} is an apocalyptic number.

It is an amenable number.

21212020102181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212020102181 is an equidigital number, since it uses as much as digits as its factorization.

21212020102181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 23.

Adding to 21212020102181 its reverse (18120102021212), we get a palindrome (39332122123393).

The spelling of 21212020102181 in words is "twenty-one trillion, two hundred twelve billion, twenty million, one hundred two thousand, one hundred eighty-one".