21984065 has 4 divisors (see below), whose sum is σ = 26380884. Its totient is φ = 17587248.

The previous prime is 21983999. The next prime is 21984073. The reversal of 21984065 is 56048912.

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 2421136 + 19562929 = 1556^2 + 4423^2 .

It is a cyclic number.

It is not a de Polignac number, because 21984065 - 2¹⁰ = 21983041 is a prime.

It is a super-2 number, since 2×21984065² = 966598227848450, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon 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 3 ways as a sum of consecutive naturals, for example, 2198402 + ... + 2198411.

It is an arithmetic number, because the mean of its divisors is an integer number (6595221).

Almost surely, 2^21984065 is an apocalyptic number.

It is an amenable number.

21984065 is a deficient number, since it is larger than the sum of its proper divisors (4396819).

21984065 is an equidigital number, since it uses as much as digits as its factorization.

21984065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4396818.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21984065 is about 4688.7167754088. The cubic root of 21984065 is about 280.1362644573.

The spelling of 21984065 in words is "twenty-one million, nine hundred eighty-four thousand, sixty-five".