21680247 has 8 divisors (see below), whose sum is σ = 29115520. Its totient is φ = 14349240.

The previous prime is 21680231. The next prime is 21680249. The reversal of 21680247 is 74208612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21680247 - 2⁴ = 21680231 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680249) 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 7 ways as a sum of consecutive naturals, for example, 25579 + ... + 26412.

It is an arithmetic number, because the mean of its divisors is an integer number (3639440).

Almost surely, 2^21680247 is an apocalyptic number.

21680247 is a deficient number, since it is larger than the sum of its proper divisors (7435273).

21680247 is a wasteful number, since it uses less digits than its factorization.

21680247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52133.

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 21680247 is about 4656.2052145497. The cubic root of 21680247 is about 278.8397867437.

Adding to 21680247 its reverse (74208612), we get a palindrome (95888859).

The spelling of 21680247 in words is "twenty-one million, six hundred eighty thousand, two hundred forty-seven".