21004045 has 4 divisors (see below), whose sum is σ = 25204860. Its totient is φ = 16803232.

The previous prime is 21004043. The next prime is 21004057. The reversal of 21004045 is 54040012.

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 13638249 + 7365796 = 3693^2 + 2714^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004045 - 2¹ = 21004043 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21004043) 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, 2100400 + ... + 2100409.

It is an arithmetic number, because the mean of its divisors is an integer number (6301215).

Almost surely, 2^21004045 is an apocalyptic number.

It is an amenable number.

21004045 is a deficient number, since it is larger than the sum of its proper divisors (4200815).

21004045 is an equidigital number, since it uses as much as digits as its factorization.

21004045 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4200814.

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21004045 is about 4583.0170193880. The cubic root of 21004045 is about 275.9101305458.

Adding to 21004045 its reverse (54040012), we get a palindrome (75044057).

The spelling of 21004045 in words is "twenty-one million, four thousand, forty-five".