21903881 has 4 divisors (see below), whose sum is σ = 22438164. Its totient is φ = 21369600.

The previous prime is 21903857. The next prime is 21903901. The reversal of 21903881 is 18830912.

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 9765625 + 12138256 = 3125^2 + 3484^2 .

It is a cyclic number.

It is not a de Polignac number, because 21903881 - 2¹⁰ = 21902857 is a prime.

It is a super-2 number, since 2×21903881² = 959560005724322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21903811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 267080 + ... + 267161.

It is an arithmetic number, because the mean of its divisors is an integer number (5609541).

Almost surely, 2^21903881 is an apocalyptic number.

It is an amenable number.

21903881 is a deficient number, since it is larger than the sum of its proper divisors (534283).

21903881 is an equidigital number, since it uses as much as digits as its factorization.

21903881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534282.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 21903881 is about 4680.1582238211. The cubic root of 21903881 is about 279.7952627467.

The spelling of 21903881 in words is "twenty-one million, nine hundred three thousand, eight hundred eighty-one".