21051305 has 8 divisors (see below), whose sum is σ = 27558144. Its totient is φ = 15310000.

The previous prime is 21051271. The next prime is 21051311. The reversal of 21051305 is 50315012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21051305 - 2⁶ = 21051241 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 191321 + ... + 191430.

It is an arithmetic number, because the mean of its divisors is an integer number (3444768).

Almost surely, 2^21051305 is an apocalyptic number.

It is an amenable number.

21051305 is a deficient number, since it is larger than the sum of its proper divisors (6506839).

21051305 is a wasteful number, since it uses less digits than its factorization.

21051305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 382767.

The product of its (nonzero) digits is 150, while the sum is 17.

The square root of 21051305 is about 4588.1701145446. The cubic root of 21051305 is about 276.1169120674.

Adding to 21051305 its reverse (50315012), we get a palindrome (71366317).

It can be divided in two parts, 210 and 51305, that added together give a palindrome (51515).

The spelling of 21051305 in words is "twenty-one million, fifty-one thousand, three hundred five".