21004217 has 8 divisors (see below), whose sum is σ = 22930824. Its totient is φ = 19122048.

The previous prime is 21004211. The next prime is 21004237. The reversal of 21004217 is 71240012.

It can be written as a sum of positive squares in 4 ways, for example, as 1032256 + 19971961 = 1016^2 + 4469^2 .

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 21004217 - 2⁶ = 21004153 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21004195 and 21004204.

It is not an unprimeable number, because it can be changed into a prime (21004211) 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, 10118 + ... + 12015.

It is an arithmetic number, because the mean of its divisors is an integer number (2866353).

Almost surely, 2^21004217 is an apocalyptic number.

It is an amenable number.

21004217 is a deficient number, since it is larger than the sum of its proper divisors (1926607).

21004217 is a wasteful number, since it uses less digits than its factorization.

21004217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22219.

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 21004217 is about 4583.0357842810. The cubic root of 21004217 is about 275.9108836771.

Adding to 21004217 its reverse (71240012), we get a palindrome (92244229).

The spelling of 21004217 in words is "twenty-one million, four thousand, two hundred seventeen".