21012143 has 4 divisors (see below), whose sum is σ = 21036720. Its totient is φ = 20987568.

The previous prime is 21012137. The next prime is 21012151. The reversal of 21012143 is 34121012.

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

It is a cyclic number.

It is not a de Polignac number, because 21012143 - 2⁴ = 21012127 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012193) 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, 10958 + ... + 12731.

It is an arithmetic number, because the mean of its divisors is an integer number (5259180).

Almost surely, 2^21012143 is an apocalyptic number.

21012143 is a deficient number, since it is larger than the sum of its proper divisors (24577).

21012143 is an equidigital number, since it uses as much as digits as its factorization.

21012143 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24576.

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

The square root of 21012143 is about 4583.9004134034. The cubic root of 21012143 is about 275.9455845604.

Adding to 21012143 its reverse (34121012), we get a palindrome (55133155).

The spelling of 21012143 in words is "twenty-one million, twelve thousand, one hundred forty-three".