21728143 has 2 divisors, whose sum is σ = 21728144. Its totient is φ = 21728142.

The previous prime is 21728129. The next prime is 21728149. The reversal of 21728143 is 34182712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21728143 - 2⁵ = 21728111 is a prime.

It is a super-2 number, since 2×21728143² = 944224396456898, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21728149) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10864071 + 10864072.

It is an arithmetic number, because the mean of its divisors is an integer number (10864072).

Almost surely, 2^21728143 is an apocalyptic number.

21728143 is a deficient number, since it is larger than the sum of its proper divisors (1).

21728143 is an equidigital number, since it uses as much as digits as its factorization.

21728143 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 28.

The square root of 21728143 is about 4661.3456211699. The cubic root of 21728143 is about 279.0449733302.

The spelling of 21728143 in words is "twenty-one million, seven hundred twenty-eight thousand, one hundred forty-three".