21122261 has 4 divisors (see below), whose sum is σ = 21138252. Its totient is φ = 21106272.

The previous prime is 21122251. The next prime is 21122267. The reversal of 21122261 is 16222112.

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 14205361 + 6916900 = 3769^2 + 2630^2 .

It is a cyclic number.

It is not a de Polignac number, because 21122261 - 2⁶ = 21122197 is a prime.

It is a super-2 number, since 2×21122261² = 892299819504242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5816 + ... + 8721.

It is an arithmetic number, because the mean of its divisors is an integer number (5284563).

Almost surely, 2^21122261 is an apocalyptic number.

It is an amenable number.

21122261 is a deficient number, since it is larger than the sum of its proper divisors (15991).

21122261 is a wasteful number, since it uses less digits than its factorization.

21122261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15990.

The product of its digits is 96, while the sum is 17.

The square root of 21122261 is about 4595.8961041346. The cubic root of 21122261 is about 276.4267927796.

Adding to 21122261 its reverse (16222112), we get a palindrome (37344373).

The spelling of 21122261 in words is "twenty-one million, one hundred twenty-two thousand, two hundred sixty-one".