21052091 has 2 divisors, whose sum is σ = 21052092. Its totient is φ = 21052090.

The previous prime is 21052081. The next prime is 21052111. The reversal of 21052091 is 19025012.

It is an a-pointer prime, because the next prime (21052111) can be obtained adding 21052091 to its sum of digits (20).

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21052091 is a prime.

It is not a weakly prime, because it can be changed into another prime (21052051) 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, 10526045 + 10526046.

It is an arithmetic number, because the mean of its divisors is an integer number (10526046).

Almost surely, 2^21052091 is an apocalyptic number.

21052091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21052091 is an equidigital number, since it uses as much as digits as its factorization.

21052091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 21052091 is about 4588.2557688080. The cubic root of 21052091 is about 276.1203485162.

The spelling of 21052091 in words is "twenty-one million, fifty-two thousand, ninety-one".