21101220181 has 2 divisors, whose sum is σ = 21101220182. Its totient is φ = 21101220180.

The previous prime is 21101220167. The next prime is 21101220209. The reversal of 21101220181 is 18102210112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20060189956 + 1041030225 = 141634^2 + 32265^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101220181 - 2²⁷ = 20967002453 is a prime.

It is a super-2 number, since 2×21101220181² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101230181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550610090 + 10550610091.

It is an arithmetic number, because the mean of its divisors is an integer number (10550610091).

Almost surely, 2^21101220181 is an apocalyptic number.

It is an amenable number.

21101220181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101220181 is an equidigital number, since it uses as much as digits as its factorization.

21101220181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64, while the sum is 19.

Adding to 21101220181 its reverse (18102210112), we get a palindrome (39203430293).

The spelling of 21101220181 in words is "twenty-one billion, one hundred one million, two hundred twenty thousand, one hundred eighty-one".