21678847 has 4 divisors (see below), whose sum is σ = 21688576. Its totient is φ = 21669120.

The previous prime is 21678823. The next prime is 21678907. The reversal of 21678847 is 74887612.

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 21678847 - 2¹¹ = 21676799 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 (21678347) 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, 322 + ... + 6592.

It is an arithmetic number, because the mean of its divisors is an integer number (5422144).

Almost surely, 2^21678847 is an apocalyptic number.

21678847 is a deficient number, since it is larger than the sum of its proper divisors (9729).

21678847 is an equidigital number, since it uses as much as digits as its factorization.

21678847 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9728.

The product of its digits is 150528, while the sum is 43.

The square root of 21678847 is about 4656.0548751062. The cubic root of 21678847 is about 278.8337845965.

The spelling of 21678847 in words is "twenty-one million, six hundred seventy-eight thousand, eight hundred forty-seven".