21886621 has 4 divisors (see below), whose sum is σ = 21896512. Its totient is φ = 21876732.

The previous prime is 21886609. The next prime is 21886637. The reversal of 21886621 is 12668812.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21886621 - 2⁷ = 21886493 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 (21886681) 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, 70 + ... + 6616.

It is an arithmetic number, because the mean of its divisors is an integer number (5474128).

Almost surely, 2^21886621 is an apocalyptic number.

It is an amenable number.

21886621 is a deficient number, since it is larger than the sum of its proper divisors (9891).

21886621 is an equidigital number, since it uses as much as digits as its factorization.

21886621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9890.

The product of its digits is 9216, while the sum is 34.

The square root of 21886621 is about 4678.3139056716. The cubic root of 21886621 is about 279.7217516451.

The spelling of 21886621 in words is "twenty-one million, eight hundred eighty-six thousand, six hundred twenty-one".