21443381 has 4 divisors (see below), whose sum is σ = 22572000. Its totient is φ = 20314764.

The previous prime is 21443363. The next prime is 21443431. The reversal of 21443381 is 18334412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21443381 - 2¹⁰ = 21442357 is a prime.

It is a super-2 number, since 2×21443381² = 919637177422322, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21443381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21443311) 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, 564281 + ... + 564318.

It is an arithmetic number, because the mean of its divisors is an integer number (5643000).

Almost surely, 2^21443381 is an apocalyptic number.

It is an amenable number.

21443381 is a deficient number, since it is larger than the sum of its proper divisors (1128619).

21443381 is a wasteful number, since it uses less digits than its factorization.

21443381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1128618.

The product of its digits is 2304, while the sum is 26.

The square root of 21443381 is about 4630.6998391172. The cubic root of 21443381 is about 277.8205845081.

Adding to 21443381 its reverse (18334412), we get a palindrome (39777793).

The spelling of 21443381 in words is "twenty-one million, four hundred forty-three thousand, three hundred eighty-one".