21219985 has 4 divisors (see below), whose sum is σ = 25463988. Its totient is φ = 16975984.

The previous prime is 21219977. The next prime is 21219997. The reversal of 21219985 is 58991212.

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 12552849 + 8667136 = 3543^2 + 2944^2 .

It is a cyclic number.

It is not a de Polignac number, because 21219985 - 2³ = 21219977 is a prime.

It is a Duffinian number.

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, 2121994 + ... + 2122003.

It is an arithmetic number, because the mean of its divisors is an integer number (6365997).

Almost surely, 2^21219985 is an apocalyptic number.

It is an amenable number.

21219985 is a deficient number, since it is larger than the sum of its proper divisors (4244003).

21219985 is an equidigital number, since it uses as much as digits as its factorization.

21219985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4244002.

The product of its digits is 12960, while the sum is 37.

The square root of 21219985 is about 4606.5154943840. The cubic root of 21219985 is about 276.8524413168.

The spelling of 21219985 in words is "twenty-one million, two hundred nineteen thousand, nine hundred eighty-five".