21248666 has 4 divisors (see below), whose sum is σ = 31873002. Its totient is φ = 10624332.

The previous prime is 21248663. The next prime is 21248687. The reversal of 21248666 is 66684212.

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

It can be written as a sum of positive squares in only one way, i.e., 13801225 + 7447441 = 3715^2 + 2729^2 .

It is not an unprimeable number, because it can be changed into a prime (21248663) 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, 5312165 + ... + 5312168.

Almost surely, 2^21248666 is an apocalyptic number.

21248666 is a deficient number, since it is larger than the sum of its proper divisors (10624336).

21248666 is a wasteful number, since it uses less digits than its factorization.

21248666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10624335.

The product of its digits is 27648, while the sum is 35.

The square root of 21248666 is about 4609.6275337602. The cubic root of 21248666 is about 276.9771167132.

The spelling of 21248666 in words is "twenty-one million, two hundred forty-eight thousand, six hundred sixty-six".