21967221 has 4 divisors (see below), whose sum is σ = 29289632. Its totient is φ = 14644812.

The previous prime is 21967199. The next prime is 21967229. The reversal of 21967221 is 12276912.

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 not a de Polignac number, because 21967221 - 2⁶ = 21967157 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 (21967229) 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, 3661201 + ... + 3661206.

It is an arithmetic number, because the mean of its divisors is an integer number (7322408).

Almost surely, 2^21967221 is an apocalyptic number.

It is an amenable number.

21967221 is a deficient number, since it is larger than the sum of its proper divisors (7322411).

21967221 is an equidigital number, since it uses as much as digits as its factorization.

21967221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7322410.

The product of its digits is 3024, while the sum is 30.

The square root of 21967221 is about 4686.9202041426. The cubic root of 21967221 is about 280.0647001845.

The spelling of 21967221 in words is "twenty-one million, nine hundred sixty-seven thousand, two hundred twenty-one".