21884381 has 4 divisors (see below), whose sum is σ = 21919164. Its totient is φ = 21849600.

The previous prime is 21884351. The next prime is 21884383. The reversal of 21884381 is 18348812.

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 15960025 + 5924356 = 3995^2 + 2434^2 .

It is a cyclic number.

It is not a de Polignac number, because 21884381 - 2¹⁰ = 21883357 is a prime.

It is a super-2 number, since 2×21884381² = 957852263506322, 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 (21884383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16430 + ... + 17711.

It is an arithmetic number, because the mean of its divisors is an integer number (5479791).

Almost surely, 2^21884381 is an apocalyptic number.

It is an amenable number.

21884381 is a deficient number, since it is larger than the sum of its proper divisors (34783).

21884381 is an equidigital number, since it uses as much as digits as its factorization.

21884381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34782.

The product of its digits is 12288, while the sum is 35.

The square root of 21884381 is about 4678.0744970554. The cubic root of 21884381 is about 279.7122085533.

The spelling of 21884381 in words is "twenty-one million, eight hundred eighty-four thousand, three hundred eighty-one".