21406305 has 16 divisors (see below), whose sum is σ = 35086464. Its totient is φ = 11137920.

The previous prime is 21406279. The next prime is 21406339. The reversal of 21406305 is 50360412.

It is a happy number.

It is not a de Polignac number, because 21406305 - 2⁶ = 21406241 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16789 + ... + 18018.

It is an arithmetic number, because the mean of its divisors is an integer number (2192904).

Almost surely, 2^21406305 is an apocalyptic number.

It is an amenable number.

21406305 is a deficient number, since it is larger than the sum of its proper divisors (13680159).

21406305 is a wasteful number, since it uses less digits than its factorization.

21406305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34856.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21406305 is about 4626.6948246021. The cubic root of 21406305 is about 277.6603731703.

Adding to 21406305 its reverse (50360412), we get a palindrome (71766717).

The spelling of 21406305 in words is "twenty-one million, four hundred six thousand, three hundred five".