21665368 has 8 divisors (see below), whose sum is σ = 40622580. Its totient is φ = 10832680.

The previous prime is 21665363. The next prime is 21665383. The reversal of 21665368 is 86356612.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665363) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1354078 + ... + 1354093.

Almost surely, 2^21665368 is an apocalyptic number.

It is an amenable number.

21665368 is a deficient number, since it is larger than the sum of its proper divisors (18957212).

21665368 is a wasteful number, since it uses less digits than its factorization.

21665368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2708177 (or 2708173 counting only the distinct ones).

The product of its digits is 51840, while the sum is 37.

The square root of 21665368 is about 4654.6071799884. The cubic root of 21665368 is about 278.7759835552.

The spelling of 21665368 in words is "twenty-one million, six hundred sixty-five thousand, three hundred sixty-eight".