21143021 has 4 divisors (see below), whose sum is σ = 21714492. Its totient is φ = 20571552.

The previous prime is 21143009. The next prime is 21143039. The reversal of 21143021 is 12034112.

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 19669225 + 1473796 = 4435^2 + 1214^2 .

It is a cyclic number.

It is not a de Polignac number, because 21143021 - 2¹⁸ = 20880877 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 = 21142987 and 21143005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21143051) 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, 285680 + ... + 285753.

It is an arithmetic number, because the mean of its divisors is an integer number (5428623).

Almost surely, 2^21143021 is an apocalyptic number.

It is an amenable number.

21143021 is a deficient number, since it is larger than the sum of its proper divisors (571471).

21143021 is an equidigital number, since it uses as much as digits as its factorization.

21143021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 571470.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21143021 is about 4598.1540861524. The cubic root of 21143021 is about 276.5173250886.

Adding to 21143021 its reverse (12034112), we get a palindrome (33177133).

The spelling of 21143021 in words is "twenty-one million, one hundred forty-three thousand, twenty-one".