21071247 has 16 divisors (see below), whose sum is σ = 30264960. Its totient is φ = 12997152.

The previous prime is 21071221. The next prime is 21071249. The reversal of 21071247 is 74217012.

It is not a de Polignac number, because 21071247 - 2⁷ = 21071119 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21071249) 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 15 ways as a sum of consecutive naturals, for example, 1848 + ... + 6749.

It is an arithmetic number, because the mean of its divisors is an integer number (1891560).

Almost surely, 2^21071247 is an apocalyptic number.

21071247 is a deficient number, since it is larger than the sum of its proper divisors (9193713).

21071247 is a wasteful number, since it uses less digits than its factorization.

21071247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8662.

The product of its (nonzero) digits is 784, while the sum is 24.

The square root of 21071247 is about 4590.3427976568. The cubic root of 21071247 is about 276.2040734992.

Adding to 21071247 its reverse (74217012), we get a palindrome (95288259).

The spelling of 21071247 in words is "twenty-one million, seventy-one thousand, two hundred forty-seven".