21224661 has 4 divisors (see below), whose sum is σ = 28299552. Its totient is φ = 14149772.

The previous prime is 21224659. The next prime is 21224689. The reversal of 21224661 is 16642212.

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 21224661 - 2¹ = 21224659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21224761) 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, 3537441 + ... + 3537446.

It is an arithmetic number, because the mean of its divisors is an integer number (7074888).

Almost surely, 2^21224661 is an apocalyptic number.

It is an amenable number.

21224661 is a deficient number, since it is larger than the sum of its proper divisors (7074891).

21224661 is an equidigital number, since it uses as much as digits as its factorization.

21224661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7074890.

The product of its digits is 1152, while the sum is 24.

The square root of 21224661 is about 4607.0230084079. The cubic root of 21224661 is about 276.8727754018.

Adding to 21224661 its reverse (16642212), we get a palindrome (37866873).

The spelling of 21224661 in words is "twenty-one million, two hundred twenty-four thousand, six hundred sixty-one".