21047709 has 8 divisors (see below), whose sum is σ = 28822240. Its totient is φ = 13652496.

The previous prime is 21047671. The next prime is 21047713. The reversal of 21047709 is 90774012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21047709 - 2⁹ = 21047197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21047209) 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 7 ways as a sum of consecutive naturals, for example, 94699 + ... + 94920.

It is an arithmetic number, because the mean of its divisors is an integer number (3602780).

Almost surely, 2^21047709 is an apocalyptic number.

It is an amenable number.

21047709 is a deficient number, since it is larger than the sum of its proper divisors (7774531).

21047709 is a wasteful number, since it uses less digits than its factorization.

21047709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189659.

The product of its (nonzero) digits is 3528, while the sum is 30.

The square root of 21047709 is about 4587.7782204461. The cubic root of 21047709 is about 276.1011890048.

The spelling of 21047709 in words is "twenty-one million, forty-seven thousand, seven hundred nine".