21288461 has 2 divisors, whose sum is σ = 21288462. Its totient is φ = 21288460.

The previous prime is 21288419. The next prime is 21288473. The reversal of 21288461 is 16488212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19802500 + 1485961 = 4450^2 + 1219^2 .

It is a cyclic number.

It is not a de Polignac number, because 21288461 - 2¹⁰ = 21287437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21288481) 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, 10644230 + 10644231.

It is an arithmetic number, because the mean of its divisors is an integer number (10644231).

Almost surely, 2^21288461 is an apocalyptic number.

It is an amenable number.

21288461 is a deficient number, since it is larger than the sum of its proper divisors (1).

21288461 is an equidigital number, since it uses as much as digits as its factorization.

21288461 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6144, while the sum is 32.

The square root of 21288461 is about 4613.9420239097. The cubic root of 21288461 is about 277.1499186288.

The spelling of 21288461 in words is "twenty-one million, two hundred eighty-eight thousand, four hundred sixty-one".