21305747 has 12 divisors (see below), whose sum is σ = 22286880. Its totient is φ = 20363616.

The previous prime is 21305741. The next prime is 21305761. The reversal of 21305747 is 74750312.

It is not a de Polignac number, because 21305747 - 2¹⁶ = 21240211 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21305741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 108053 + ... + 108249.

It is an arithmetic number, because the mean of its divisors is an integer number (1857240).

Almost surely, 2^21305747 is an apocalyptic number.

21305747 is a deficient number, since it is larger than the sum of its proper divisors (981133).

21305747 is an equidigital number, since it uses as much as digits as its factorization.

21305747 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350 (or 313 counting only the distinct ones).

The product of its (nonzero) digits is 5880, while the sum is 29.

The square root of 21305747 is about 4615.8148793035. The cubic root of 21305747 is about 277.2249125795.

The spelling of 21305747 in words is "twenty-one million, three hundred five thousand, seven hundred forty-seven".