21222761 has 4 divisors (see below), whose sum is σ = 24254592. Its totient is φ = 18190932.

The previous prime is 21222757. The next prime is 21222787. The reversal of 21222761 is 16722212.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21222761 - 2² = 21222757 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21222361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1515905 + ... + 1515918.

It is an arithmetic number, because the mean of its divisors is an integer number (6063648).

Almost surely, 2^21222761 is an apocalyptic number.

It is an amenable number.

21222761 is a deficient number, since it is larger than the sum of its proper divisors (3031831).

21222761 is an equidigital number, since it uses as much as digits as its factorization.

21222761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3031830.

The product of its digits is 672, while the sum is 23.

The square root of 21222761 is about 4606.8167968783. The cubic root of 21222761 is about 276.8645134093.

Adding to 21222761 its reverse (16722212), we get a palindrome (37944973).

The spelling of 21222761 in words is "twenty-one million, two hundred twenty-two thousand, seven hundred sixty-one".