21004213 has 4 divisors (see below), whose sum is σ = 21029580. Its totient is φ = 20978848.

The previous prime is 21004211. The next prime is 21004237. The reversal of 21004213 is 31240012.

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 19421649 + 1582564 = 4407^2 + 1258^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004213 - 2¹ = 21004211 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21004193 and 21004202.

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 11398 + ... + 13111.

It is an arithmetic number, because the mean of its divisors is an integer number (5257395).

Almost surely, 2^21004213 is an apocalyptic number.

It is an amenable number.

21004213 is a deficient number, since it is larger than the sum of its proper divisors (25367).

21004213 is an equidigital number, since it uses as much as digits as its factorization.

21004213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25366.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21004213 is about 4583.0353478890. The cubic root of 21004213 is about 275.9108661625.

Adding to 21004213 its reverse (31240012), we get a palindrome (52244225).

The spelling of 21004213 in words is "twenty-one million, four thousand, two hundred thirteen".