21840347 has 4 divisors (see below), whose sum is σ = 21849696. Its totient is φ = 21831000.

The previous prime is 21840319. The next prime is 21840361. The reversal of 21840347 is 74304812.

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 21840347 - 2⁶ = 21840283 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21840047) 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 3 ways as a sum of consecutive naturals, for example, 2222 + ... + 6972.

It is an arithmetic number, because the mean of its divisors is an integer number (5462424).

Almost surely, 2^21840347 is an apocalyptic number.

21840347 is a deficient number, since it is larger than the sum of its proper divisors (9349).

21840347 is an equidigital number, since it uses as much as digits as its factorization.

21840347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9348.

The product of its (nonzero) digits is 5376, while the sum is 29.

The square root of 21840347 is about 4673.3657036444. The cubic root of 21840347 is about 279.5244777446.

The spelling of 21840347 in words is "twenty-one million, eight hundred forty thousand, three hundred forty-seven".