21664127 has 4 divisors (see below), whose sum is σ = 21738360. Its totient is φ = 21589896.

The previous prime is 21664117. The next prime is 21664141. The reversal of 21664127 is 72146612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21664127 - 2⁶ = 21664063 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21664127.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664117) 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, 36677 + ... + 37262.

It is an arithmetic number, because the mean of its divisors is an integer number (5434590).

Almost surely, 2^21664127 is an apocalyptic number.

21664127 is a deficient number, since it is larger than the sum of its proper divisors (74233).

21664127 is an equidigital number, since it uses as much as digits as its factorization.

21664127 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74232.

The product of its digits is 4032, while the sum is 29.

The square root of 21664127 is about 4654.4738693004. The cubic root of 21664127 is about 278.7706606577.

The spelling of 21664127 in words is "twenty-one million, six hundred sixty-four thousand, one hundred twenty-seven".