21208051 has 2 divisors, whose sum is σ = 21208052. Its totient is φ = 21208050.

The previous prime is 21208049. The next prime is 21208063. The reversal of 21208051 is 15080212.

21208051 is nontrivially palindromic in base 12.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21208051 - 2¹ = 21208049 is a prime.

Together with 21208049, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21208091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10604025 + 10604026.

It is an arithmetic number, because the mean of its divisors is an integer number (10604026).

Almost surely, 2^21208051 is an apocalyptic number.

21208051 is a deficient number, since it is larger than the sum of its proper divisors (1).

21208051 is an equidigital number, since it uses as much as digits as its factorization.

21208051 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 160, while the sum is 19.

The square root of 21208051 is about 4605.2199730306. The cubic root of 21208051 is about 276.8005314999.

Adding to 21208051 its reverse (15080212), we get a palindrome (36288263).

The spelling of 21208051 in words is "twenty-one million, two hundred eight thousand, fifty-one".