21642609 has 8 divisors (see below), whose sum is σ = 30111552. Its totient is φ = 13801040.

The previous prime is 21642601. The next prime is 21642637. The reversal of 21642609 is 90624612.

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 21642609 - 2³ = 21642601 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21642601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 156762 + ... + 156899.

It is an arithmetic number, because the mean of its divisors is an integer number (3763944).

Almost surely, 2^21642609 is an apocalyptic number.

It is an amenable number.

21642609 is a deficient number, since it is larger than the sum of its proper divisors (8468943).

21642609 is a wasteful number, since it uses less digits than its factorization.

21642609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 313687.

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 21642609 is about 4652.1617555713. The cubic root of 21642609 is about 278.6783333091.

The spelling of 21642609 in words is "twenty-one million, six hundred forty-two thousand, six hundred nine".