21311233 has 4 divisors (see below), whose sum is σ = 21324868. Its totient is φ = 21297600.

The previous prime is 21311219. The next prime is 21311237. The reversal of 21311233 is 33211312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12027024 + 9284209 = 3468^2 + 3047^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311233 - 2¹³ = 21303041 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21311237) 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, 4116 + ... + 7717.

It is an arithmetic number, because the mean of its divisors is an integer number (5331217).

Almost surely, 2^21311233 is an apocalyptic number.

It is an amenable number.

21311233 is a deficient number, since it is larger than the sum of its proper divisors (13635).

21311233 is a wasteful number, since it uses less digits than its factorization.

21311233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13634.

The product of its digits is 108, while the sum is 16.

The square root of 21311233 is about 4616.4091023218. The cubic root of 21311233 is about 277.2487046789.

Adding to 21311233 its reverse (33211312), we get a palindrome (54522545).

It can be divided in two parts, 2131 and 1233, that added together give a square (3364 = 58²).

The spelling of 21311233 in words is "twenty-one million, three hundred eleven thousand, two hundred thirty-three".