21804147 has 24 divisors (see below), whose sum is σ = 33297264. Its totient is φ = 14253408.

The previous prime is 21804131. The next prime is 21804179. The reversal of 21804147 is 74140812.

It is not a de Polignac number, because 21804147 - 2⁴ = 21804131 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21804147.

It is not an unprimeable number, because it can be changed into a prime (21804187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12033 + ... + 13725.

It is an arithmetic number, because the mean of its divisors is an integer number (1387386).

Almost surely, 2^21804147 is an apocalyptic number.

21804147 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21804147 is a deficient number, since it is larger than the sum of its proper divisors (11493117).

21804147 is an equidigital number, since it uses as much as digits as its factorization.

21804147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1761 (or 1749 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 27.

The square root of 21804147 is about 4669.4910857608. The cubic root of 21804147 is about 279.3699566677.

Adding to 21804147 its reverse (74140812), we get a palindrome (95944959).

The spelling of 21804147 in words is "twenty-one million, eight hundred four thousand, one hundred forty-seven".