21450181 has 2 divisors, whose sum is σ = 21450182. Its totient is φ = 21450180.

The previous prime is 21450179. The next prime is 21450211. The reversal of 21450181 is 18105412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20557156 + 893025 = 4534^2 + 945^2 .

It is a cyclic number.

It is not a de Polignac number, because 21450181 - 2¹ = 21450179 is a prime.

It is a super-2 number, since 2×21450181² = 920220529865522, which contains 22 as substring.

Together with 21450179, it forms a pair of twin primes.

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 (21450161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10725090 + 10725091.

It is an arithmetic number, because the mean of its divisors is an integer number (10725091).

Almost surely, 2^21450181 is an apocalyptic number.

It is an amenable number.

21450181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21450181 is an equidigital number, since it uses as much as digits as its factorization.

21450181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 320, while the sum is 22.

The square root of 21450181 is about 4631.4340111892. The cubic root of 21450181 is about 277.8499483526.

Adding to 21450181 its reverse (18105412), we get a palindrome (39555593).

The spelling of 21450181 in words is "twenty-one million, four hundred fifty thousand, one hundred eighty-one".