20165661 has 6 divisors (see below), whose sum is σ = 29128190. Its totient is φ = 13443768.

The previous prime is 20165659. The next prime is 20165671. The reversal of 20165661 is 16656102.

It is a happy number.

20165661 is a `hidden beast` number, since 2 + 0 + 1 + 656 + 6 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 17589636 + 2576025 = 4194^2 + 1605^2 .

It is not a de Polignac number, because 20165661 - 2¹ = 20165659 is a prime.

It is a super-3 number, since 3×20165661³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20165611) 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 5 ways as a sum of consecutive naturals, for example, 1120306 + ... + 1120323.

Almost surely, 2^20165661 is an apocalyptic number.

It is an amenable number.

20165661 is a deficient number, since it is larger than the sum of its proper divisors (8962529).

20165661 is a wasteful number, since it uses less digits than its factorization.

20165661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2240635 (or 2240632 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 20165661 is about 4490.6192223345. The cubic root of 20165661 is about 272.1891570989.

The spelling of 20165661 in words is "twenty million, one hundred sixty-five thousand, six hundred sixty-one".