21131611 has 4 divisors (see below), whose sum is σ = 21238000. Its totient is φ = 21025224.

The previous prime is 21131597. The next prime is 21131651. The reversal of 21131611 is 11613112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21131611 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131651) 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, 52896 + ... + 53293.

It is an arithmetic number, because the mean of its divisors is an integer number (5309500).

Almost surely, 2^21131611 is an apocalyptic number.

21131611 is a deficient number, since it is larger than the sum of its proper divisors (106389).

21131611 is a wasteful number, since it uses less digits than its factorization.

21131611 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106388.

The product of its digits is 36, while the sum is 16.

The square root of 21131611 is about 4596.9132034442. The cubic root of 21131611 is about 276.4675745444.

Adding to 21131611 its reverse (11613112), we get a palindrome (32744723).

It can be divided in two parts, 2113 and 1611, that multiplied together give a palindrome (3404043).

The spelling of 21131611 in words is "twenty-one million, one hundred thirty-one thousand, six hundred eleven".