21804481 has 2 divisors, whose sum is σ = 21804482. Its totient is φ = 21804480.

The previous prime is 21804479. The next prime is 21804487. The reversal of 21804481 is 18440812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21307456 + 497025 = 4616^2 + 705^2 .

It is a cyclic number.

It is not a de Polignac number, because 21804481 - 2¹ = 21804479 is a prime.

It is a super-2 number, since 2×21804481² = 950870783358722, which contains 22 as substring.

Together with 21804479, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21804487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10902240 + 10902241.

It is an arithmetic number, because the mean of its divisors is an integer number (10902241).

Almost surely, 2^21804481 is an apocalyptic number.

It is an amenable number.

21804481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21804481 is an equidigital number, since it uses as much as digits as its factorization.

21804481 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2048, while the sum is 28.

The square root of 21804481 is about 4669.5268496926. The cubic root of 21804481 is about 279.3713831408.

The spelling of 21804481 in words is "twenty-one million, eight hundred four thousand, four hundred eighty-one".