20391205 has 8 divisors (see below), whose sum is σ = 25313400. Its totient is φ = 15750336.

The previous prime is 20391197. The next prime is 20391221. The reversal of 20391205 is 50219302.

It can be written as a sum of positive squares in 4 ways, for example, as 8892324 + 11498881 = 2982^2 + 3391^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20391205 - 2³ = 20391197 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 70170 + ... + 70459.

It is an arithmetic number, because the mean of its divisors is an integer number (3164175).

Almost surely, 2^20391205 is an apocalyptic number.

It is an amenable number.

20391205 is a deficient number, since it is larger than the sum of its proper divisors (4922195).

20391205 is a wasteful number, since it uses less digits than its factorization.

20391205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140663.

The product of its (nonzero) digits is 540, while the sum is 22.

The square root of 20391205 is about 4515.6621884282. The cubic root of 20391205 is about 273.2001689571.

The spelling of 20391205 in words is "twenty million, three hundred ninety-one thousand, two hundred five".