21008465 has 8 divisors (see below), whose sum is σ = 25309800. Its totient is φ = 16740352.

The previous prime is 21008459. The next prime is 21008497. The reversal of 21008465 is 56480012.

It can be written as a sum of positive squares in 4 ways, for example, as 4231249 + 16777216 = 2057^2 + 4096^2 .

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 21008465 - 2⁶ = 21008401 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6890 + ... + 9459.

It is an arithmetic number, because the mean of its divisors is an integer number (3163725).

Almost surely, 2^21008465 is an apocalyptic number.

It is an amenable number.

21008465 is a deficient number, since it is larger than the sum of its proper divisors (4301335).

21008465 is a wasteful number, since it uses less digits than its factorization.

21008465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16611.

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21008465 is about 4583.4992091196. The cubic root of 21008465 is about 275.9294829649.

Adding to 21008465 its reverse (56480012), we get a palindrome (77488477).

The spelling of 21008465 in words is "twenty-one million, eight thousand, four hundred sixty-five".