21747071 has 4 divisors (see below), whose sum is σ = 22497000. Its totient is φ = 20997144.

The previous prime is 21747059. The next prime is 21747073. The reversal of 21747071 is 17074712.

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

It is a cyclic number.

It is not a de Polignac number, because 21747071 - 2⁶ = 21747007 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 749899 = 21747071 / (2 + 1 + 7 + 4 + 7 + 0 + 7 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21747073) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 374921 + ... + 374978.

It is an arithmetic number, because the mean of its divisors is an integer number (5624250).

Almost surely, 2^21747071 is an apocalyptic number.

21747071 is a deficient number, since it is larger than the sum of its proper divisors (749929).

21747071 is an equidigital number, since it uses as much as digits as its factorization.

21747071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 749928.

The product of its (nonzero) digits is 2744, while the sum is 29.

The square root of 21747071 is about 4663.3754942102. The cubic root of 21747071 is about 279.1259778029.

The spelling of 21747071 in words is "twenty-one million, seven hundred forty-seven thousand, seventy-one".