21027921 has 4 divisors (see below), whose sum is σ = 28037232. Its totient is φ = 14018612.

The previous prime is 21027913. The next prime is 21027931. The reversal of 21027921 is 12972012.

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 21027921 - 2³ = 21027913 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21027891 and 21027900.

It is not an unprimeable number, because it can be changed into a prime (21027931) 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, 3504651 + ... + 3504656.

It is an arithmetic number, because the mean of its divisors is an integer number (7009308).

Almost surely, 2^21027921 is an apocalyptic number.

It is an amenable number.

21027921 is a deficient number, since it is larger than the sum of its proper divisors (7009311).

21027921 is an equidigital number, since it uses as much as digits as its factorization.

21027921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7009310.

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 21027921 is about 4585.6211138732. The cubic root of 21027921 is about 276.0146363799.

Adding to 21027921 its reverse (12972012), we get a palindrome (33999933).

The spelling of 21027921 in words is "twenty-one million, twenty-seven thousand, nine hundred twenty-one".