21023872 has 16 divisors (see below), whose sum is σ = 41883750. Its totient is φ = 10511872.

The previous prime is 21023867. The next prime is 21023879. The reversal of 21023872 is 27832012.

It can be written as a sum of positive squares in only one way, i.e., 21013056 + 10816 = 4584^2 + 104^2 .

It is a tau number, because it is divible by the number of its divisors (16).

It is not an unprimeable number, because it can be changed into a prime (21023879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 81997 + ... + 82252.

Almost surely, 2^21023872 is an apocalyptic number.

It is an amenable number.

21023872 is a deficient number, since it is larger than the sum of its proper divisors (20859878).

21023872 is an equidigital number, since it uses as much as digits as its factorization.

21023872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164263 (or 164251 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21023872 is about 4585.1796038978. The cubic root of 21023872 is about 275.9969193803.

Adding to 21023872 its reverse (27832012), we get a palindrome (48855884).

The spelling of 21023872 in words is "twenty-one million, twenty-three thousand, eight hundred seventy-two".