21120709 has 4 divisors (see below), whose sum is σ = 21237580. Its totient is φ = 21003840.

The previous prime is 21120707. The next prime is 21120713. The reversal of 21120709 is 90702112.

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 9628609 + 11492100 = 3103^2 + 3390^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120709 - 2¹ = 21120707 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21120709.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120707) 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, 58164 + ... + 58525.

It is an arithmetic number, because the mean of its divisors is an integer number (5309395).

Almost surely, 2^21120709 is an apocalyptic number.

It is an amenable number.

21120709 is a deficient number, since it is larger than the sum of its proper divisors (116871).

21120709 is a wasteful number, since it uses less digits than its factorization.

21120709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116870.

The product of its (nonzero) digits is 252, while the sum is 22.

The square root of 21120709 is about 4595.7272547443. The cubic root of 21120709 is about 276.4200222783.

The spelling of 21120709 in words is "twenty-one million, one hundred twenty thousand, seven hundred nine".