21020555 has 16 divisors (see below), whose sum is σ = 26666400. Its totient is φ = 15863040.

The previous prime is 21020543. The next prime is 21020581. The reversal of 21020555 is 55502012.

It is not a de Polignac number, because 21020555 - 2⁸ = 21020299 is a prime.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 38585 + ... + 39125.

It is an arithmetic number, because the mean of its divisors is an integer number (1666650).

Almost surely, 2^21020555 is an apocalyptic number.

21020555 is a deficient number, since it is larger than the sum of its proper divisors (5645845).

21020555 is a wasteful number, since it uses less digits than its factorization.

21020555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 974.

The product of its (nonzero) digits is 500, while the sum is 20.

The square root of 21020555 is about 4584.8178807887. The cubic root of 21020555 is about 275.9824036601.

Adding to 21020555 its reverse (55502012), we get a palindrome (76522567).

The spelling of 21020555 in words is "twenty-one million, twenty thousand, five hundred fifty-five".