21051055 has 4 divisors (see below), whose sum is σ = 25261272. Its totient is φ = 16840840.

The previous prime is 21051047. The next prime is 21051059. The reversal of 21051055 is 55015012.

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

It is not a de Polignac number, because 21051055 - 2³ = 21051047 is a prime.

It is a super-2 number, since 2×21051055² = 886293833226050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051059) 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, 2105101 + ... + 2105110.

It is an arithmetic number, because the mean of its divisors is an integer number (6315318).

Almost surely, 2^21051055 is an apocalyptic number.

21051055 is a deficient number, since it is larger than the sum of its proper divisors (4210217).

21051055 is an equidigital number, since it uses as much as digits as its factorization.

21051055 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4210216.

The product of its (nonzero) digits is 250, while the sum is 19.

The square root of 21051055 is about 4588.1428704869. The cubic root of 21051055 is about 276.1158190314.

Adding to 21051055 its reverse (55015012), we get a palindrome (76066067).

It can be divided in two parts, 2105 and 1055, that added together give a triangular number (3160 = T₇₉).

The spelling of 21051055 in words is "twenty-one million, fifty-one thousand, fifty-five".