21055481 has 4 divisors (see below), whose sum is σ = 21064692. Its totient is φ = 21046272.

The previous prime is 21055471. The next prime is 21055501. The reversal of 21055481 is 18455012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 13542400 + 7513081 = 3680^2 + 2741^2 .

It is a cyclic number.

It is not a de Polignac number, because 21055481 - 2¹⁰ = 21054457 is a prime.

It is a super-2 number, since 2×21055481² = 886666560282722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21055481.

It is not an unprimeable number, because it can be changed into a prime (21055451) 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, 1721 + ... + 6713.

It is an arithmetic number, because the mean of its divisors is an integer number (5266173).

Almost surely, 2^21055481 is an apocalyptic number.

It is an amenable number.

21055481 is a deficient number, since it is larger than the sum of its proper divisors (9211).

21055481 is an equidigital number, since it uses as much as digits as its factorization.

21055481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9210.

The product of its (nonzero) digits is 1600, while the sum is 26.

The square root of 21055481 is about 4588.6251753657. The cubic root of 21055481 is about 276.1351688610.

The spelling of 21055481 in words is "twenty-one million, fifty-five thousand, four hundred eighty-one".