21253117 has 2 divisors, whose sum is σ = 21253118. Its totient is φ = 21253116.

The previous prime is 21253109. The next prime is 21253121. The reversal of 21253117 is 71135212.

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., 11431161 + 9821956 = 3381^2 + 3134^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253117 - 2³ = 21253109 is a prime.

It is equal to p_1344901 and since 21253117 and 1344901 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21253217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10626558 + 10626559.

It is an arithmetic number, because the mean of its divisors is an integer number (10626559).

Almost surely, 2^21253117 is an apocalyptic number.

It is an amenable number.

21253117 is a deficient number, since it is larger than the sum of its proper divisors (1).

21253117 is an equidigital number, since it uses as much as digits as its factorization.

21253117 is an evil number, because the sum of its binary digits is even.

The product of its digits is 420, while the sum is 22.

The square root of 21253117 is about 4610.1103023680. The cubic root of 21253117 is about 276.9964550107.

Adding to 21253117 its reverse (71135212), we get a palindrome (92388329).

The spelling of 21253117 in words is "twenty-one million, two hundred fifty-three thousand, one hundred seventeen".