21424805 has 8 divisors (see below), whose sum is σ = 25811352. Its totient is φ = 17072128.

The previous prime is 21424787. The next prime is 21424829. The reversal of 21424805 is 50842412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 13410244 + 8014561 = 3662^2 + 2831^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21424805 - 2⁸ = 21424549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 7052 + ... + 9621.

It is an arithmetic number, because the mean of its divisors is an integer number (3226419).

Almost surely, 2^21424805 is an apocalyptic number.

It is an amenable number.

21424805 is a deficient number, since it is larger than the sum of its proper divisors (4386547).

21424805 is a wasteful number, since it uses less digits than its factorization.

21424805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16935.

The product of its (nonzero) digits is 2560, while the sum is 26.

The square root of 21424805 is about 4628.6936602026. The cubic root of 21424805 is about 277.7403377391.

The spelling of 21424805 in words is "twenty-one million, four hundred twenty-four thousand, eight hundred five".