21583381 has 2 divisors, whose sum is σ = 21583382. Its totient is φ = 21583380.

The previous prime is 21583379. The next prime is 21583423. The reversal of 21583381 is 18338512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21298225 + 285156 = 4615^2 + 534^2 .

It is a cyclic number.

It is not a de Polignac number, because 21583381 - 2¹ = 21583379 is a prime.

It is a super-2 number, since 2×21583381² = 931684670782322, which contains 22 as substring.

Together with 21583379, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21583181) 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 as a sum of consecutive naturals, namely, 10791690 + 10791691.

It is an arithmetic number, because the mean of its divisors is an integer number (10791691).

Almost surely, 2^21583381 is an apocalyptic number.

It is an amenable number.

21583381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21583381 is an equidigital number, since it uses as much as digits as its factorization.

21583381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5760, while the sum is 31.

The square root of 21583381 is about 4645.7917516824. The cubic root of 21583381 is about 278.4238870939.

The spelling of 21583381 in words is "twenty-one million, five hundred eighty-three thousand, three hundred eighty-one".