21068381 has 4 divisors (see below), whose sum is σ = 21081564. Its totient is φ = 21055200.

The previous prime is 21068357. The next prime is 21068417. The reversal of 21068381 is 18386012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 511225 + 20557156 = 715^2 + 4534^2 .

It is a cyclic number.

It is not a de Polignac number, because 21068381 - 2⁶ = 21068317 is a prime.

It is a super-2 number, since 2×21068381² = 887753355922322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065381) 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 in 3 ways as a sum of consecutive naturals, for example, 3800 + ... + 7521.

It is an arithmetic number, because the mean of its divisors is an integer number (5270391).

Almost surely, 2^21068381 is an apocalyptic number.

It is an amenable number.

21068381 is a deficient number, since it is larger than the sum of its proper divisors (13183).

21068381 is a wasteful number, since it uses less digits than its factorization.

21068381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13182.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21068381 is about 4590.0306099197. The cubic root of 21068381 is about 276.1915503238.

The spelling of 21068381 in words is "twenty-one million, sixty-eight thousand, three hundred eighty-one".