21728867 has 2 divisors, whose sum is σ = 21728868. Its totient is φ = 21728866.

The previous prime is 21728857. The next prime is 21728891. The reversal of 21728867 is 76882712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21728867 - 2⁴ = 21728851 is a prime.

It is a super-2 number, since 2×21728867² = 944287322207378, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21728807) 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 as a sum of consecutive naturals, namely, 10864433 + 10864434.

It is an arithmetic number, because the mean of its divisors is an integer number (10864434).

Almost surely, 2^21728867 is an apocalyptic number.

21728867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21728867 is an equidigital number, since it uses as much as digits as its factorization.

21728867 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 75264, while the sum is 41.

The square root of 21728867 is about 4661.4232805014. The cubic root of 21728867 is about 279.0480726335.

The spelling of 21728867 in words is "twenty-one million, seven hundred twenty-eight thousand, eight hundred sixty-seven".