21312605 has 8 divisors (see below), whose sum is σ = 26687232. Its totient is φ = 16308688.

The previous prime is 21312587. The next prime is 21312619. The reversal of 21312605 is 50621312.

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 21312605 - 2¹² = 21308509 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 92549 + ... + 92778.

It is an arithmetic number, because the mean of its divisors is an integer number (3335904).

Almost surely, 2^21312605 is an apocalyptic number.

It is an amenable number.

21312605 is a deficient number, since it is larger than the sum of its proper divisors (5374627).

21312605 is a wasteful number, since it uses less digits than its factorization.

21312605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185355.

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

The square root of 21312605 is about 4616.5577002784. The cubic root of 21312605 is about 277.2546542340.

Adding to 21312605 its reverse (50621312), we get a palindrome (71933917).

The spelling of 21312605 in words is "twenty-one million, three hundred twelve thousand, six hundred five".