21305409 has 8 divisors (see below), whose sum is σ = 28873152. Its totient is φ = 13970640.

The previous prime is 21305399. The next prime is 21305413. The reversal of 21305409 is 90450312.

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

It is not a de Polignac number, because 21305409 - 2⁹ = 21304897 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21305419) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 58029 + ... + 58394.

It is an arithmetic number, because the mean of its divisors is an integer number (3609144).

Almost surely, 2^21305409 is an apocalyptic number.

It is an amenable number.

21305409 is a deficient number, since it is larger than the sum of its proper divisors (7567743).

21305409 is a wasteful number, since it uses less digits than its factorization.

21305409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116487.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 21305409 is about 4615.7782659049. The cubic root of 21305409 is about 277.2234465820.

The spelling of 21305409 in words is "twenty-one million, three hundred five thousand, four hundred nine".