21185247 has 16 divisors (see below), whose sum is σ = 31484160. Its totient is φ = 12592512.

The previous prime is 21185243. The next prime is 21185249. The reversal of 21185247 is 74258112.

It is not a de Polignac number, because 21185247 - 2² = 21185243 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21185243) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9963 + ... + 11900.

It is an arithmetic number, because the mean of its divisors is an integer number (1967760).

Almost surely, 2^21185247 is an apocalyptic number.

21185247 is a deficient number, since it is larger than the sum of its proper divisors (10298913).

21185247 is a wasteful number, since it uses less digits than its factorization.

21185247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21902.

The product of its digits is 4480, while the sum is 30.

The square root of 21185247 is about 4602.7434210479. The cubic root of 21185247 is about 276.7012858084.

It can be divided in two parts, 211 and 85247, that added together give a palindrome (85458).

The spelling of 21185247 in words is "twenty-one million, one hundred eighty-five thousand, two hundred forty-seven".