21421305 has 12 divisors (see below), whose sum is σ = 37130340. Its totient is φ = 11424672.

The previous prime is 21421273. The next prime is 21421319. The reversal of 21421305 is 50312412.

It can be written as a sum of positive squares in 2 ways, for example, as 3196944 + 18224361 = 1788^2 + 4269^2 .

It is not a de Polignac number, because 21421305 - 2⁵ = 21421273 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 237970 + ... + 238059.

It is an arithmetic number, because the mean of its divisors is an integer number (3094195).

Almost surely, 2^21421305 is an apocalyptic number.

It is an amenable number.

21421305 is a deficient number, since it is larger than the sum of its proper divisors (15709035).

21421305 is a wasteful number, since it uses less digits than its factorization.

21421305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 476040 (or 476037 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21421305 is about 4628.3155683250. The cubic root of 21421305 is about 277.7252128388.

Adding to 21421305 its reverse (50312412), we get a palindrome (71733717).

The spelling of 21421305 in words is "twenty-one million, four hundred twenty-one thousand, three hundred five".