21738609 has 12 divisors (see below), whose sum is σ = 31933200. Its totient is φ = 14246424.

The previous prime is 21738599. The next prime is 21738617. The reversal of 21738609 is 90683712.

21738609 is a `hidden beast` number, since 2 + 17 + 38 + 609 = 666.

It is not a de Polignac number, because 21738609 - 2⁴ = 21738593 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21738659) 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 11 ways as a sum of consecutive naturals, for example, 19939 + ... + 21000.

It is an arithmetic number, because the mean of its divisors is an integer number (2661100).

Almost surely, 2^21738609 is an apocalyptic number.

It is an amenable number.

21738609 is a deficient number, since it is larger than the sum of its proper divisors (10194591).

21738609 is a wasteful number, since it uses less digits than its factorization.

21738609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41004 (or 41001 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21738609 is about 4662.4681232154. The cubic root of 21738609 is about 279.0897695484.

The spelling of 21738609 in words is "twenty-one million, seven hundred thirty-eight thousand, six hundred nine".