20165821 has 12 divisors (see below), whose sum is σ = 22925532. Its totient is φ = 17630784.

The previous prime is 20165819. The next prime is 20165843. The reversal of 20165821 is 12856102.

It can be written as a sum of positive squares in 2 ways, for example, as 6579225 + 13586596 = 2565^2 + 3686^2 .

It is not a de Polignac number, because 20165821 - 2¹ = 20165819 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 (20165801) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2545 + ... + 6841.

It is an arithmetic number, because the mean of its divisors is an integer number (1910461).

Almost surely, 2^20165821 is an apocalyptic number.

It is an amenable number.

20165821 is a deficient number, since it is larger than the sum of its proper divisors (2759711).

20165821 is a wasteful number, since it uses less digits than its factorization.

20165821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4348 (or 4329 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 20165821 is about 4490.6370372142. The cubic root of 20165821 is about 272.1898769720.

The spelling of 20165821 in words is "twenty million, one hundred sixty-five thousand, eight hundred twenty-one".