21938665 has 16 divisors (see below), whose sum is σ = 31396608. Its totient is φ = 14389056.

The previous prime is 21938663. The next prime is 21938699. The reversal of 21938665 is 56683912.

It is a cyclic number.

It is not a de Polignac number, because 21938665 - 2¹ = 21938663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21938663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12822 + ... + 14431.

It is an arithmetic number, because the mean of its divisors is an integer number (1962288).

Almost surely, 2^21938665 is an apocalyptic number.

It is an amenable number.

21938665 is a deficient number, since it is larger than the sum of its proper divisors (9457943).

21938665 is a wasteful number, since it uses less digits than its factorization.

21938665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27288.

The product of its digits is 77760, while the sum is 40.

The square root of 21938665 is about 4683.8728633472. The cubic root of 21938665 is about 279.9432920872.

The spelling of 21938665 in words is "twenty-one million, nine hundred thirty-eight thousand, six hundred sixty-five".