21165355 has 4 divisors (see below), whose sum is σ = 25398432. Its totient is φ = 16932280.

The previous prime is 21165299. The next prime is 21165379. The reversal of 21165355 is 55356112.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21165355 - 2⁷ = 21165227 is a prime.

It is a Duffinian number.

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 3 ways as a sum of consecutive naturals, for example, 2116531 + ... + 2116540.

It is an arithmetic number, because the mean of its divisors is an integer number (6349608).

Almost surely, 2^21165355 is an apocalyptic number.

21165355 is a deficient number, since it is larger than the sum of its proper divisors (4233077).

21165355 is an equidigital number, since it uses as much as digits as its factorization.

21165355 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4233076.

The product of its digits is 4500, while the sum is 28.

The square root of 21165355 is about 4600.5820283960. The cubic root of 21165355 is about 276.6146553089.

It can be divided in two parts, 2116 and 5355, that multiplied together give a triangular number (11331180 = T₄₇₆₀).

The spelling of 21165355 in words is "twenty-one million, one hundred sixty-five thousand, three hundred fifty-five".