21003247 has 2 divisors, whose sum is σ = 21003248. Its totient is φ = 21003246.

The previous prime is 21003223. The next prime is 21003259. The reversal of 21003247 is 74230012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21003247 - 2²³ = 12614639 is a prime.

It is a super-2 number, since 2×21003247² = 882272769086018, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21003547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501623 + 10501624.

It is an arithmetic number, because the mean of its divisors is an integer number (10501624).

Almost surely, 2^21003247 is an apocalyptic number.

21003247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21003247 is an equidigital number, since it uses as much as digits as its factorization.

21003247 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 336, while the sum is 19.

The square root of 21003247 is about 4582.9299580072. The cubic root of 21003247 is about 275.9066363129.

Adding to 21003247 its reverse (74230012), we get a palindrome (95233259).

The spelling of 21003247 in words is "twenty-one million, three thousand, two hundred forty-seven".