21107664 has 30 divisors (see below), whose sum is σ = 59072546. Its totient is φ = 7035840.

The previous prime is 21107641. The next prime is 21107699. The reversal of 21107664 is 46670112.

It can be written as a sum of positive squares in only one way, i.e., 17139600 + 3968064 = 4140^2 + 1992^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 73147 + ... + 73434.

Almost surely, 2^21107664 is an apocalyptic number.

21107664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21107664 is an abundant number, since it is smaller than the sum of its proper divisors (37964882).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21107664 is a wasteful number, since it uses less digits than its factorization.

21107664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146595 (or 146586 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21107664 is about 4594.3077824630. The cubic root of 21107664 is about 276.3631011804.

Adding to 21107664 its reverse (46670112), we get a palindrome (67777776).

The spelling of 21107664 in words is "twenty-one million, one hundred seven thousand, six hundred sixty-four".