21010664 has 16 divisors (see below), whose sum is σ = 39984000. Its totient is φ = 10348272.

The previous prime is 21010663. The next prime is 21010673. The reversal of 21010664 is 46601012.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21010663) 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, 19064 + ... + 20135.

It is an arithmetic number, because the mean of its divisors is an integer number (2499000).

Almost surely, 2^21010664 is an apocalyptic number.

It is an amenable number.

21010664 is a deficient number, since it is larger than the sum of its proper divisors (18973336).

21010664 is a wasteful number, since it uses less digits than its factorization.

21010664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39272 (or 39268 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21010664 is about 4583.7390850702. The cubic root of 21010664 is about 275.9391100011.

Adding to 21010664 its reverse (46601012), we get a palindrome (67611676).

The spelling of 21010664 in words is "twenty-one million, ten thousand, six hundred sixty-four".