21340709 has 4 divisors (see below), whose sum is σ = 22982316. Its totient is φ = 19699104.

The previous prime is 21340663. The next prime is 21340721. The reversal of 21340709 is 90704312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7672900 + 13667809 = 2770^2 + 3697^2 .

It is a cyclic number.

It is not a de Polignac number, because 21340709 - 2¹² = 21336613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21340769) 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, 820784 + ... + 820809.

It is an arithmetic number, because the mean of its divisors is an integer number (5745579).

Almost surely, 2^21340709 is an apocalyptic number.

It is an amenable number.

21340709 is a deficient number, since it is larger than the sum of its proper divisors (1641607).

21340709 is a wasteful number, since it uses less digits than its factorization.

21340709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1641606.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 21340709 is about 4619.6005238548. The cubic root of 21340709 is about 277.3764685677.

The spelling of 21340709 in words is "twenty-one million, three hundred forty thousand, seven hundred nine".