21551273 has 2 divisors, whose sum is σ = 21551274. Its totient is φ = 21551272.

The previous prime is 21551267. The next prime is 21551297. The reversal of 21551273 is 37215512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20187049 + 1364224 = 4493^2 + 1168^2 .

It is a cyclic number.

It is not a de Polignac number, because 21551273 - 2¹⁴ = 21534889 is a prime.

It is not a weakly prime, because it can be changed into another prime (21551573) 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, 10775636 + 10775637.

It is an arithmetic number, because the mean of its divisors is an integer number (10775637).

Almost surely, 2^21551273 is an apocalyptic number.

It is an amenable number.

21551273 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551273 is an equidigital number, since it uses as much as digits as its factorization.

21551273 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2100, while the sum is 26.

The square root of 21551273 is about 4642.3348651298. The cubic root of 21551273 is about 278.2857550317.

Adding to 21551273 its reverse (37215512), we get a palindrome (58766785).

The spelling of 21551273 in words is "twenty-one million, five hundred fifty-one thousand, two hundred seventy-three".