21313261 has 4 divisors (see below), whose sum is σ = 21715452. Its totient is φ = 20911072.

The previous prime is 21313247. The next prime is 21313283. The reversal of 21313261 is 16231312.

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 6220036 + 15093225 = 2494^2 + 3885^2 .

It is a cyclic number.

It is not a de Polignac number, because 21313261 - 2⁷ = 21313133 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21313241) 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, 201016 + ... + 201121.

It is an arithmetic number, because the mean of its divisors is an integer number (5428863).

Almost surely, 2^21313261 is an apocalyptic number.

It is an amenable number.

21313261 is a deficient number, since it is larger than the sum of its proper divisors (402191).

21313261 is an equidigital number, since it uses as much as digits as its factorization.

21313261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 402190.

The product of its digits is 216, while the sum is 19.

The square root of 21313261 is about 4616.6287483401. The cubic root of 21313261 is about 277.2574988289.

Adding to 21313261 its reverse (16231312), we get a palindrome (37544573).

The spelling of 21313261 in words is "twenty-one million, three hundred thirteen thousand, two hundred sixty-one".