21041021 has 4 divisors (see below), whose sum is σ = 21955872. Its totient is φ = 20126172.

The previous prime is 21041011. The next prime is 21041029. The reversal of 21041021 is 12014012.

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 21041021 - 2¹⁴ = 21024637 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21040993 and 21041011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21041029) 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, 457391 + ... + 457436.

It is an arithmetic number, because the mean of its divisors is an integer number (5488968).

Almost surely, 2^21041021 is an apocalyptic number.

It is an amenable number.

21041021 is a deficient number, since it is larger than the sum of its proper divisors (914851).

21041021 is an equidigital number, since it uses as much as digits as its factorization.

21041021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 914850.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 21041021 is about 4587.0492694106. The cubic root of 21041021 is about 276.0719417936.

Adding to 21041021 its reverse (12014012), we get a palindrome (33055033).

It can be divided in two parts, 2104 and 1021, that added together give a 5-th power (3125 = 5⁵).

The spelling of 21041021 in words is "twenty-one million, forty-one thousand, twenty-one".