21004245 has 32 divisors (see below), whose sum is σ = 37616640. Its totient is φ = 11119680.

The previous prime is 21004241. The next prime is 21004261. The reversal of 21004245 is 54240012.

It is not a de Polignac number, because 21004245 - 2² = 21004241 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21004241) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 20700 + ... + 21690.

It is an arithmetic number, because the mean of its divisors is an integer number (1175520).

Almost surely, 2^21004245 is an apocalyptic number.

It is an amenable number.

21004245 is a deficient number, since it is larger than the sum of its proper divisors (16612395).

21004245 is a wasteful number, since it uses less digits than its factorization.

21004245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1162 (or 1156 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21004245 is about 4583.0388390237. The cubic root of 21004245 is about 275.9110062795.

Adding to 21004245 its reverse (54240012), we get a palindrome (75244257).

The spelling of 21004245 in words is "twenty-one million, four thousand, two hundred forty-five".