21818149 has 2 divisors, whose sum is σ = 21818150. Its totient is φ = 21818148.

The previous prime is 21818129. The next prime is 21818171. The reversal of 21818149 is 94181812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21095649 + 722500 = 4593^2 + 850^2 .

It is a cyclic number.

It is not a de Polignac number, because 21818149 - 2⁵ = 21818117 is a prime.

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 (21818119) 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, 10909074 + 10909075.

It is an arithmetic number, because the mean of its divisors is an integer number (10909075).

Almost surely, 2^21818149 is an apocalyptic number.

It is an amenable number.

21818149 is a deficient number, since it is larger than the sum of its proper divisors (1).

21818149 is an equidigital number, since it uses as much as digits as its factorization.

21818149 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4608, while the sum is 34.

The square root of 21818149 is about 4670.9901519913. The cubic root of 21818149 is about 279.4297450051.

The spelling of 21818149 in words is "twenty-one million, eight hundred eighteen thousand, one hundred forty-nine".