21605006 has 8 divisors (see below), whose sum is σ = 33161304. Its totient is φ = 10551240.

The previous prime is 21604997. The next prime is 21605009. The reversal of 21605006 is 60050612.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605009) 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, 125525 + ... + 125696.

It is an arithmetic number, because the mean of its divisors is an integer number (4145163).

Almost surely, 2^21605006 is an apocalyptic number.

21605006 is a deficient number, since it is larger than the sum of its proper divisors (11556298).

21605006 is a wasteful number, since it uses less digits than its factorization.

21605006 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251266.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21605006 is about 4648.1185440993. The cubic root of 21605006 is about 278.5168429787.

Adding to 21605006 its reverse (60050612), we get a palindrome (81655618).

The spelling of 21605006 in words is "twenty-one million, six hundred five thousand, six".