21716647 has 4 divisors (see below), whose sum is σ = 22417216. Its totient is φ = 21016080.

The previous prime is 21716627. The next prime is 21716659. The reversal of 21716647 is 74661712.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21716647 is a prime.

It is a super-2 number, since 2×21716647² = 943225513845218, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21716627) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 350238 + ... + 350299.

It is an arithmetic number, because the mean of its divisors is an integer number (5604304).

Almost surely, 2^21716647 is an apocalyptic number.

21716647 is a deficient number, since it is larger than the sum of its proper divisors (700569).

21716647 is an equidigital number, since it uses as much as digits as its factorization.

21716647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 700568.

The product of its digits is 14112, while the sum is 34.

The square root of 21716647 is about 4660.1123377017. The cubic root of 21716647 is about 278.9957519597.

The spelling of 21716647 in words is "twenty-one million, seven hundred sixteen thousand, six hundred forty-seven".