21646139 has 2 divisors, whose sum is σ = 21646140. Its totient is φ = 21646138.

The previous prime is 21646129. The next prime is 21646189. The reversal of 21646139 is 93164612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21646139 - 2⁴ = 21646123 is a prime.

It is not a weakly prime, because it can be changed into another prime (21646129) 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, 10823069 + 10823070.

It is an arithmetic number, because the mean of its divisors is an integer number (10823070).

Almost surely, 2^21646139 is an apocalyptic number.

21646139 is a deficient number, since it is larger than the sum of its proper divisors (1).

21646139 is an equidigital number, since it uses as much as digits as its factorization.

21646139 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7776, while the sum is 32.

The square root of 21646139 is about 4652.5411336172. The cubic root of 21646139 is about 278.6934836858.

The spelling of 21646139 in words is "twenty-one million, six hundred forty-six thousand, one hundred thirty-nine".