21257299 has 4 divisors (see below), whose sum is σ = 24294064. Its totient is φ = 18220536.

The previous prime is 21257297. The next prime is 21257303. The reversal of 21257299 is 99275212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21257299 - 2¹ = 21257297 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21257297) 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 in 3 ways as a sum of consecutive naturals, for example, 1518372 + ... + 1518385.

It is an arithmetic number, because the mean of its divisors is an integer number (6073516).

Almost surely, 2^21257299 is an apocalyptic number.

21257299 is a deficient number, since it is larger than the sum of its proper divisors (3036765).

21257299 is an equidigital number, since it uses as much as digits as its factorization.

21257299 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3036764.

The product of its digits is 22680, while the sum is 37.

The square root of 21257299 is about 4610.5638483812. The cubic root of 21257299 is about 277.0146221217.

The spelling of 21257299 in words is "twenty-one million, two hundred fifty-seven thousand, two hundred ninety-nine".