21287753 has 2 divisors, whose sum is σ = 21287754. Its totient is φ = 21287752.

The previous prime is 21287741. The next prime is 21287759. The reversal of 21287753 is 35778212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15077689 + 6210064 = 3883^2 + 2492^2 .

It is a cyclic number.

It is not a de Polignac number, because 21287753 - 2⁴ = 21287737 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21287759) 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, 10643876 + 10643877.

It is an arithmetic number, because the mean of its divisors is an integer number (10643877).

Almost surely, 2^21287753 is an apocalyptic number.

It is an amenable number.

21287753 is a deficient number, since it is larger than the sum of its proper divisors (1).

21287753 is an equidigital number, since it uses as much as digits as its factorization.

21287753 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23520, while the sum is 35.

The square root of 21287753 is about 4613.8652992908. The cubic root of 21287753 is about 277.1468461613.

The spelling of 21287753 in words is "twenty-one million, two hundred eighty-seven thousand, seven hundred fifty-three".