21262261 has 4 divisors (see below), whose sum is σ = 21271500. Its totient is φ = 21253024.

The previous prime is 21262247. The next prime is 21262289. The reversal of 21262261 is 16226212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 6200100 + 15062161 = 2490^2 + 3881^2 .

It is a cyclic number.

It is not a de Polignac number, because 21262261 - 2⁵ = 21262229 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 (21262211) 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, 1905 + ... + 6793.

It is an arithmetic number, because the mean of its divisors is an integer number (5317875).

Almost surely, 2^21262261 is an apocalyptic number.

It is an amenable number.

21262261 is a deficient number, since it is larger than the sum of its proper divisors (9239).

21262261 is an equidigital number, since it uses as much as digits as its factorization.

21262261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9238.

The product of its digits is 576, while the sum is 22.

The square root of 21262261 is about 4611.1019290404. The cubic root of 21262261 is about 277.0361745559.

Adding to 21262261 its reverse (16226212), we get a palindrome (37488473).

The spelling of 21262261 in words is "twenty-one million, two hundred sixty-two thousand, two hundred sixty-one".