20665751 has 4 divisors (see below), whose sum is σ = 20744592. Its totient is φ = 20586912.

The previous prime is 20665741. The next prime is 20665769. The reversal of 20665751 is 15756602.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 15756602 = 2 ⋅7878301.

It is a cyclic number.

It is not a de Polignac number, because 20665751 - 2¹⁰ = 20664727 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20665741) 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, 39026 + ... + 39551.

It is an arithmetic number, because the mean of its divisors is an integer number (5186148).

Almost surely, 2^20665751 is an apocalyptic number.

20665751 is a deficient number, since it is larger than the sum of its proper divisors (78841).

20665751 is an equidigital number, since it uses as much as digits as its factorization.

20665751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78840.

The product of its (nonzero) digits is 12600, while the sum is 32.

The square root of 20665751 is about 4545.9598546402. The cubic root of 20665751 is about 274.4208240323.

The spelling of 20665751 in words is "twenty million, six hundred sixty-five thousand, seven hundred fifty-one".