21609047 has 8 divisors (see below), whose sum is σ = 21857472. Its totient is φ = 21362400.

The previous prime is 21609037. The next prime is 21609053. The reversal of 21609047 is 74090612.

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 21609047 - 2¹⁴ = 21592663 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 (21609017) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49922 + ... + 50352.

It is an arithmetic number, because the mean of its divisors is an integer number (2732184).

Almost surely, 2^21609047 is an apocalyptic number.

21609047 is a deficient number, since it is larger than the sum of its proper divisors (248425).

21609047 is a wasteful number, since it uses less digits than its factorization.

21609047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 889.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 21609047 is about 4648.5532157866. The cubic root of 21609047 is about 278.5342064916.

Adding to 21609047 its reverse (74090612), we get a palindrome (95699659).

The spelling of 21609047 in words is "twenty-one million, six hundred nine thousand, forty-seven".