21287248 has 10 divisors (see below), whose sum is σ = 41244074. Its totient is φ = 10643616.

The previous prime is 21287243. The next prime is 21287249. The reversal of 21287248 is 84278212.

It can be written as a sum of positive squares in only one way, i.e., 17239104 + 4048144 = 4152^2 + 2012^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 665211 + ... + 665242.

Almost surely, 2^21287248 is an apocalyptic number.

It is an amenable number.

21287248 is a deficient number, since it is larger than the sum of its proper divisors (19956826).

21287248 is a wasteful number, since it uses less digits than its factorization.

21287248 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1330461 (or 1330455 counting only the distinct ones).

The product of its digits is 14336, while the sum is 34.

The square root of 21287248 is about 4613.8105726178. The cubic root of 21287248 is about 277.1446545997.

The spelling of 21287248 in words is "twenty-one million, two hundred eighty-seven thousand, two hundred forty-eight".