21709609 has 8 divisors (see below), whose sum is σ = 22900640. Its totient is φ = 20523456.

The previous prime is 21709601. The next prime is 21709613. The reversal of 21709609 is 90690712.

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

It is a cyclic number.

It is not a de Polignac number, because 21709609 - 2³ = 21709601 is a prime.

It is a super-3 number, since 3×21709609³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21709601) 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, 11329 + ... + 13105.

It is an arithmetic number, because the mean of its divisors is an integer number (2862580).

Almost surely, 2^21709609 is an apocalyptic number.

It is an amenable number.

21709609 is a deficient number, since it is larger than the sum of its proper divisors (1191031).

21709609 is a wasteful number, since it uses less digits than its factorization.

21709609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2439.

The product of its (nonzero) digits is 6804, while the sum is 34.

The square root of 21709609 is about 4659.3571444997. The cubic root of 21709609 is about 278.9656094265.

The spelling of 21709609 in words is "twenty-one million, seven hundred nine thousand, six hundred nine".