21204767 has 4 divisors (see below), whose sum is σ = 21215160. Its totient is φ = 21194376.

The previous prime is 21204739. The next prime is 21204787. The reversal of 21204767 is 76740212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21204767 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204707) 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, 1013 + ... + 6590.

It is an arithmetic number, because the mean of its divisors is an integer number (5303790).

Almost surely, 2^21204767 is an apocalyptic number.

21204767 is a deficient number, since it is larger than the sum of its proper divisors (10393).

21204767 is an equidigital number, since it uses as much as digits as its factorization.

21204767 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10392.

The product of its (nonzero) digits is 4704, while the sum is 29.

The square root of 21204767 is about 4604.8634073119. The cubic root of 21204767 is about 276.7862435318.

Adding to 21204767 its reverse (76740212), we get a palindrome (97944979).

The spelling of 21204767 in words is "twenty-one million, two hundred four thousand, seven hundred sixty-seven".