21424705 has 4 divisors (see below), whose sum is σ = 25709652. Its totient is φ = 17139760.

The previous prime is 21424699. The next prime is 21424759. The reversal of 21424705 is 50742412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13307904 + 8116801 = 3648^2 + 2849^2 .

It is not a de Polignac number, because 21424705 - 2⁷ = 21424577 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21424705.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2142466 + ... + 2142475.

It is an arithmetic number, because the mean of its divisors is an integer number (6427413).

Almost surely, 2^21424705 is an apocalyptic number.

It is an amenable number.

21424705 is a deficient number, since it is larger than the sum of its proper divisors (4284947).

21424705 is an equidigital number, since it uses as much as digits as its factorization.

21424705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4284946.

The product of its (nonzero) digits is 2240, while the sum is 25.

The square root of 21424705 is about 4628.6828580062. The cubic root of 21424705 is about 277.7399056219.

The spelling of 21424705 in words is "twenty-one million, four hundred twenty-four thousand, seven hundred five".