21664121 has 8 divisors (see below), whose sum is σ = 22227264. Its totient is φ = 21106800.

The previous prime is 21664117. The next prime is 21664141. The reversal of 21664121 is 12146612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21664121 - 2² = 21664117 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21664141) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6650 + ... + 9356.

It is an arithmetic number, because the mean of its divisors is an integer number (2778408).

Almost surely, 2^21664121 is an apocalyptic number.

It is an amenable number.

21664121 is a deficient number, since it is larger than the sum of its proper divisors (563143).

21664121 is a wasteful number, since it uses less digits than its factorization.

21664121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2911.

The product of its digits is 576, while the sum is 23.

The square root of 21664121 is about 4654.4732247592. The cubic root of 21664121 is about 278.7706349220.

The spelling of 21664121 in words is "twenty-one million, six hundred sixty-four thousand, one hundred twenty-one".