20121865 has 8 divisors (see below), whose sum is σ = 24175368. Its totient is φ = 16078080.

The previous prime is 20121841. The next prime is 20121869. The reversal of 20121865 is 56812102.

It can be written as a sum of positive squares in 4 ways, for example, as 1042441 + 19079424 = 1021^2 + 4368^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20121865 - 2¹³ = 20113673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20121869) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3409 + ... + 7201.

It is an arithmetic number, because the mean of its divisors is an integer number (3021921).

Almost surely, 2^20121865 is an apocalyptic number.

It is an amenable number.

20121865 is a deficient number, since it is larger than the sum of its proper divisors (4053503).

20121865 is a wasteful number, since it uses less digits than its factorization.

20121865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4859.

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

The square root of 20121865 is about 4485.7401841837. The cubic root of 20121865 is about 271.9919664943.

Adding to 20121865 its reverse (56812102), we get a palindrome (76933967).

The spelling of 20121865 in words is "twenty million, one hundred twenty-one thousand, eight hundred sixty-five".