21231611 has 2 divisors, whose sum is σ = 21231612. Its totient is φ = 21231610.

The previous prime is 21231601. The next prime is 21231629. The reversal of 21231611 is 11613212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21231611 - 2⁶ = 21231547 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21231611.

It is not a weakly prime, because it can be changed into another prime (21231601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615805 + 10615806.

It is an arithmetic number, because the mean of its divisors is an integer number (10615806).

Almost surely, 2^21231611 is an apocalyptic number.

21231611 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231611 is an equidigital number, since it uses as much as digits as its factorization.

21231611 is an evil number, because the sum of its binary digits is even.

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

The square root of 21231611 is about 4607.7772298582. Note that the first 3 decimals coincide. The cubic root of 21231611 is about 276.9029927010.

Adding to 21231611 its reverse (11613212), we get a palindrome (32844823).

The spelling of 21231611 in words is "twenty-one million, two hundred thirty-one thousand, six hundred eleven".