21312611 has 4 divisors (see below), whose sum is σ = 22566312. Its totient is φ = 20058912.

The previous prime is 21312587. The next prime is 21312619. The reversal of 21312611 is 11621312.

It is a semiprime because it is the product of two primes.

It is a de Polignac number, because none of the positive numbers 2^k-21312611 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17), and also a Moran number because the ratio is a prime number: 1253683 = 21312611 / (2 + 1 + 3 + 1 + 2 + 6 + 1 + 1).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21312611.

It is not an unprimeable number, because it can be changed into a prime (21312619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 626825 + ... + 626858.

It is an arithmetic number, because the mean of its divisors is an integer number (5641578).

Almost surely, 2^21312611 is an apocalyptic number.

21312611 is a deficient number, since it is larger than the sum of its proper divisors (1253701).

21312611 is a wasteful number, since it uses less digits than its factorization.

21312611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1253700.

The product of its digits is 72, while the sum is 17.

The square root of 21312611 is about 4616.5583501132. The cubic root of 21312611 is about 277.2546802519.

Adding to 21312611 its reverse (11621312), we get a palindrome (32933923).

The spelling of 21312611 in words is "twenty-one million, three hundred twelve thousand, six hundred eleven".