21280417 has 2 divisors, whose sum is σ = 21280418. Its totient is φ = 21280416.

The previous prime is 21280409. The next prime is 21280423. The reversal of 21280417 is 71408212.

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., 13220496 + 8059921 = 3636^2 + 2839^2 .

It is a cyclic number.

It is not a de Polignac number, because 21280417 - 2³ = 21280409 is a prime.

It is a super-2 number, since 2×21280417² = 905712295387778, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21280391 and 21280400.

It is not a weakly prime, because it can be changed into another prime (21280487) 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, 10640208 + 10640209.

It is an arithmetic number, because the mean of its divisors is an integer number (10640209).

Almost surely, 2^21280417 is an apocalyptic number.

It is an amenable number.

21280417 is a deficient number, since it is larger than the sum of its proper divisors (1).

21280417 is an equidigital number, since it uses as much as digits as its factorization.

21280417 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 21280417 is about 4613.0702357541. The cubic root of 21280417 is about 277.1150065262.

Adding to 21280417 its reverse (71408212), we get a palindrome (92688629).

The spelling of 21280417 in words is "twenty-one million, two hundred eighty thousand, four hundred seventeen".