21128137 has 2 divisors, whose sum is σ = 21128138. Its totient is φ = 21128136.

The previous prime is 21128131. The next prime is 21128167. The reversal of 21128137 is 73182112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19882681 + 1245456 = 4459^2 + 1116^2 .

It is a cyclic number.

It is not a de Polignac number, because 21128137 - 2¹¹ = 21126089 is a prime.

It is not a weakly prime, because it can be changed into another prime (21128131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10564068 + 10564069.

It is an arithmetic number, because the mean of its divisors is an integer number (10564069).

Almost surely, 2^21128137 is an apocalyptic number.

It is an amenable number.

21128137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21128137 is an equidigital number, since it uses as much as digits as its factorization.

21128137 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 672, while the sum is 25.

The square root of 21128137 is about 4596.5353256556. The cubic root of 21128137 is about 276.4524234517.

The spelling of 21128137 in words is "twenty-one million, one hundred twenty-eight thousand, one hundred thirty-seven".