21180847 has 4 divisors (see below), whose sum is σ = 21528136. Its totient is φ = 20833560.

The previous prime is 21180799. The next prime is 21180857. The reversal of 21180847 is 74808112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21180847 - 2¹⁵ = 21148079 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 (21180857) 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 3 ways as a sum of consecutive naturals, for example, 173553 + ... + 173674.

It is an arithmetic number, because the mean of its divisors is an integer number (5382034).

Almost surely, 2^21180847 is an apocalyptic number.

21180847 is a deficient number, since it is larger than the sum of its proper divisors (347289).

21180847 is an equidigital number, since it uses as much as digits as its factorization.

21180847 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 347288.

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 21180847 is about 4602.2654204207. The cubic root of 21180847 is about 276.6821282951.

Adding to 21180847 its reverse (74808112), we get a palindrome (95988959).

The spelling of 21180847 in words is "twenty-one million, one hundred eighty thousand, eight hundred forty-seven".