21148709 has 2 divisors, whose sum is σ = 21148710. Its totient is φ = 21148708.

The previous prime is 21148703. The next prime is 21148717. The reversal of 21148709 is 90784112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15626209 + 5522500 = 3953^2 + 2350^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21148709 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21148703) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10574354 + 10574355.

It is an arithmetic number, because the mean of its divisors is an integer number (10574355).

Almost surely, 2^21148709 is an apocalyptic number.

It is an amenable number.

21148709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21148709 is an equidigital number, since it uses as much as digits as its factorization.

21148709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 21148709 is about 4598.7725536278. The cubic root of 21148709 is about 276.5421195511.

The spelling of 21148709 in words is "twenty-one million, one hundred forty-eight thousand, seven hundred nine".