21664330 has 16 divisors (see below), whose sum is σ = 39237984. Its totient is φ = 8611920.

The previous prime is 21664327. The next prime is 21664339. The reversal of 21664330 is 3346612.

It is a junction number, because it is equal to n+sod(n) for n = 21664295 and 21664304.

It is not an unprimeable number, because it can be changed into a prime (21664339) 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, 5016 + ... + 8275.

It is an arithmetic number, because the mean of its divisors is an integer number (2452374).

Almost surely, 2^21664330 is an apocalyptic number.

21664330 is a deficient number, since it is larger than the sum of its proper divisors (17573654).

21664330 is a wasteful number, since it uses less digits than its factorization.

21664330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13461.

The product of its (nonzero) digits is 2592, while the sum is 25.

The square root of 21664330 is about 4654.4956762253. The cubic root of 21664330 is about 278.7715313792.

It can be divided in two parts, 216 and 64330, that added together give a palindrome (64546).

The spelling of 21664330 in words is "twenty-one million, six hundred sixty-four thousand, three hundred thirty".