21642005 has 32 divisors (see below), whose sum is σ = 32901120. Its totient is φ = 13273920.

The previous prime is 21641993. The next prime is 21642013. The reversal of 21642005 is 50024612.

It is a happy number.

It is not a de Polignac number, because 21642005 - 2¹² = 21637909 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 25376 + ... + 26214.

It is an arithmetic number, because the mean of its divisors is an integer number (1028160).

Almost surely, 2^21642005 is an apocalyptic number.

It is an amenable number.

21642005 is a deficient number, since it is larger than the sum of its proper divisors (11259115).

21642005 is a wasteful number, since it uses less digits than its factorization.

21642005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 929.

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21642005 is about 4652.0968390609. The cubic root of 21642005 is about 278.6757408416.

Adding to 21642005 its reverse (50024612), we get a palindrome (71666617).

The spelling of 21642005 in words is "twenty-one million, six hundred forty-two thousand, five".