21204817 has 8 divisors (see below), whose sum is σ = 22376160. Its totient is φ = 20039040.

The previous prime is 21204803. The next prime is 21204863. The reversal of 21204817 is 71840212.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21204817 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21204791 and 21204800.

It is not an unprimeable number, because it can be changed into a prime (21204917) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8193 + ... + 10465.

It is an arithmetic number, because the mean of its divisors is an integer number (2797020).

Almost surely, 2^21204817 is an apocalyptic number.

It is an amenable number.

21204817 is a deficient number, since it is larger than the sum of its proper divisors (1171343).

21204817 is a wasteful number, since it uses less digits than its factorization.

21204817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2783.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 21204817 is about 4604.8688363514. The cubic root of 21204817 is about 276.7864610820.

The spelling of 21204817 in words is "twenty-one million, two hundred four thousand, eight hundred seventeen".