21052909 has 2 divisors, whose sum is σ = 21052910. Its totient is φ = 21052908.

The previous prime is 21052907. The next prime is 21052943. The reversal of 21052909 is 90925012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11035684 + 10017225 = 3322^2 + 3165^2 .

It is a cyclic number.

It is not a de Polignac number, because 21052909 - 2¹ = 21052907 is a prime.

Together with 21052907, it forms a pair of twin primes.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21052907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10526454 + 10526455.

It is an arithmetic number, because the mean of its divisors is an integer number (10526455).

Almost surely, 2^21052909 is an apocalyptic number.

It is an amenable number.

21052909 is a deficient number, since it is larger than the sum of its proper divisors (1).

21052909 is an equidigital number, since it uses as much as digits as its factorization.

21052909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1620, while the sum is 28.

The square root of 21052909 is about 4588.3449085700. The cubic root of 21052909 is about 276.1239247804.

The spelling of 21052909 in words is "twenty-one million, fifty-two thousand, nine hundred nine".