21204501 has 4 divisors (see below), whose sum is σ = 28272672. Its totient is φ = 14136332.

The previous prime is 21204499. The next prime is 21204509. The reversal of 21204501 is 10540212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21204501 - 2¹ = 21204499 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3534081 + ... + 3534086.

It is an arithmetic number, because the mean of its divisors is an integer number (7068168).

Almost surely, 2^21204501 is an apocalyptic number.

It is an amenable number.

21204501 is a deficient number, since it is larger than the sum of its proper divisors (7068171).

21204501 is an equidigital number, since it uses as much as digits as its factorization.

21204501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7068170.

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21204501 is about 4604.8345247142. The cubic root of 21204501 is about 276.7850861592.

Adding to 21204501 its reverse (10540212), we get a palindrome (31744713).

The spelling of 21204501 in words is "twenty-one million, two hundred four thousand, five hundred one".