21001143 has 8 divisors (see below), whose sum is σ = 28684656. Its totient is φ = 13659200.

The previous prime is 21001121. The next prime is 21001153. The reversal of 21001143 is 34110012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21001143 - 2¹² = 20997047 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001153) 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 7 ways as a sum of consecutive naturals, for example, 85248 + ... + 85493.

It is an arithmetic number, because the mean of its divisors is an integer number (3585582).

Almost surely, 2^21001143 is an apocalyptic number.

21001143 is a deficient number, since it is larger than the sum of its proper divisors (7683513).

21001143 is a wasteful number, since it uses less digits than its factorization.

21001143 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170785.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21001143 is about 4582.7004047832. The cubic root of 21001143 is about 275.8974230240.

Adding to 21001143 its reverse (34110012), we get a palindrome (55111155).

The spelling of 21001143 in words is "twenty-one million, one thousand, one hundred forty-three".