21221273 has 2 divisors, whose sum is σ = 21221274. Its totient is φ = 21221272.

The previous prime is 21221257. The next prime is 21221279. The reversal of 21221273 is 37212212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15031129 + 6190144 = 3877^2 + 2488^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221273 - 2⁴ = 21221257 is a prime.

It is not a weakly prime, because it can be changed into another prime (21221279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610636 + 10610637.

It is an arithmetic number, because the mean of its divisors is an integer number (10610637).

Almost surely, 2^21221273 is an apocalyptic number.

It is an amenable number.

21221273 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221273 is an equidigital number, since it uses as much as digits as its factorization.

21221273 is an evil number, because the sum of its binary digits is even.

The product of its digits is 336, while the sum is 20.

The square root of 21221273 is about 4606.6552942455. The cubic root of 21221273 is about 276.8580426203.

Adding to 21221273 its reverse (37212212), we get a palindrome (58433485).

The spelling of 21221273 in words is "twenty-one million, two hundred twenty-one thousand, two hundred seventy-three".