21270181 has 2 divisors, whose sum is σ = 21270182. Its totient is φ = 21270180.

The previous prime is 21270173. The next prime is 21270187. The reversal of 21270181 is 18107212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18062500 + 3207681 = 4250^2 + 1791^2 .

It is a cyclic number.

It is not a de Polignac number, because 21270181 - 2³ = 21270173 is a prime.

It is a super-2 number, since 2×21270181² = 904841199545522, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21270187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10635090 + 10635091.

It is an arithmetic number, because the mean of its divisors is an integer number (10635091).

Almost surely, 2^21270181 is an apocalyptic number.

It is an amenable number.

21270181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21270181 is an equidigital number, since it uses as much as digits as its factorization.

21270181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21270181 is about 4611.9606459726. The cubic root of 21270181 is about 277.0705681093.

Adding to 21270181 its reverse (18107212), we get a palindrome (39377393).

The spelling of 21270181 in words is "twenty-one million, two hundred seventy thousand, one hundred eighty-one".