21032021 has 4 divisors (see below), whose sum is σ = 21600492. Its totient is φ = 20463552.

The previous prime is 21032003. The next prime is 21032023. The reversal of 21032021 is 12023012.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 18748900 + 2283121 = 4330^2 + 1511^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21032021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21031993 and 21032011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21032023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 284180 + ... + 284253.

It is an arithmetic number, because the mean of its divisors is an integer number (5400123).

Almost surely, 2^21032021 is an apocalyptic number.

It is an amenable number.

21032021 is a deficient number, since it is larger than the sum of its proper divisors (568471).

21032021 is an equidigital number, since it uses as much as digits as its factorization.

21032021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 568470.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21032021 is about 4586.0681416656. The cubic root of 21032021 is about 276.0325742202.

Adding to 21032021 its reverse (12023012), we get a palindrome (33055033).

Subtracting from 21032021 its reverse (12023012), we obtain a palindrome (9009009).

The spelling of 21032021 in words is "twenty-one million, thirty-two thousand, twenty-one".