21824381 has 2 divisors, whose sum is σ = 21824382. Its totient is φ = 21824380.

The previous prime is 21824371. The next prime is 21824417. The reversal of 21824381 is 18342812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18705625 + 3118756 = 4325^2 + 1766^2 .

It is a cyclic number.

It is not a de Polignac number, because 21824381 - 2⁶ = 21824317 is a prime.

It is a super-2 number, since 2×21824381² = 952607212066322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21824371) 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, 10912190 + 10912191.

It is an arithmetic number, because the mean of its divisors is an integer number (10912191).

Almost surely, 2^21824381 is an apocalyptic number.

It is an amenable number.

21824381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21824381 is an equidigital number, since it uses as much as digits as its factorization.

21824381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3072, while the sum is 29.

The square root of 21824381 is about 4671.6572006088. The cubic root of 21824381 is about 279.4563473290.

The spelling of 21824381 in words is "twenty-one million, eight hundred twenty-four thousand, three hundred eighty-one".