21688347 has 4 divisors (see below), whose sum is σ = 28917800. Its totient is φ = 14458896.

The previous prime is 21688343. The next prime is 21688391. The reversal of 21688347 is 74388612.

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

It is not a de Polignac number, because 21688347 - 2² = 21688343 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21688343) 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, 3614722 + ... + 3614727.

It is an arithmetic number, because the mean of its divisors is an integer number (7229450).

Almost surely, 2^21688347 is an apocalyptic number.

21688347 is a deficient number, since it is larger than the sum of its proper divisors (7229453).

21688347 is an equidigital number, since it uses as much as digits as its factorization.

21688347 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7229452.

The product of its digits is 64512, while the sum is 39.

The square root of 21688347 is about 4657.0749403461. The cubic root of 21688347 is about 278.8745083815.

The spelling of 21688347 in words is "twenty-one million, six hundred eighty-eight thousand, three hundred forty-seven".