21713647 has 4 divisors (see below), whose sum is σ = 21724416. Its totient is φ = 21702880.

The previous prime is 21713639. The next prime is 21713669. The reversal of 21713647 is 74631712.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21713647 - 2³ = 21713639 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 (21713677) 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, 1354 + ... + 6727.

It is an arithmetic number, because the mean of its divisors is an integer number (5431104).

Almost surely, 2^21713647 is an apocalyptic number.

21713647 is a deficient number, since it is larger than the sum of its proper divisors (10769).

21713647 is an equidigital number, since it uses as much as digits as its factorization.

21713647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10768.

The product of its digits is 7056, while the sum is 31.

The square root of 21713647 is about 4659.7904459321. The cubic root of 21713647 is about 278.9829042766.

The spelling of 21713647 in words is "twenty-one million, seven hundred thirteen thousand, six hundred forty-seven".