21059555 has 16 divisors (see below), whose sum is σ = 27661824. Its totient is φ = 15264480.

The previous prime is 21059537. The next prime is 21059557. The reversal of 21059555 is 55595012.

It is not a de Polignac number, because 21059555 - 2¹⁴ = 21043171 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21059557) 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 15 ways as a sum of consecutive naturals, for example, 25052 + ... + 25878.

It is an arithmetic number, because the mean of its divisors is an integer number (1728864).

Almost surely, 2^21059555 is an apocalyptic number.

21059555 is a deficient number, since it is larger than the sum of its proper divisors (6602269).

21059555 is a wasteful number, since it uses less digits than its factorization.

21059555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1306.

The product of its (nonzero) digits is 11250, while the sum is 32.

The square root of 21059555 is about 4589.0690777106. The cubic root of 21059555 is about 276.1529774010.

The spelling of 21059555 in words is "twenty-one million, fifty-nine thousand, five hundred fifty-five".