20506405 has 8 divisors (see below), whose sum is σ = 24660000. Its totient is φ = 16370256.

The previous prime is 20506397. The next prime is 20506417. The reversal of 20506405 is 50460502.

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 20506405 - 2³ = 20506397 is a prime.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 1615 + ... + 6604.

It is an arithmetic number, because the mean of its divisors is an integer number (3082500).

Almost surely, 2^20506405 is an apocalyptic number.

It is an amenable number.

20506405 is a deficient number, since it is larger than the sum of its proper divisors (4153595).

20506405 is an equidigital number, since it uses as much as digits as its factorization.

20506405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8723.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 20506405 is about 4528.3998277537. The cubic root of 20506405 is about 273.7136840825.

Adding to 20506405 its reverse (50460502), we get a palindrome (70966907).

It can be divided in two parts, 2050 and 6405, that multiplied together give a triangular number (13130250 = T₅₁₂₄).

The spelling of 20506405 in words is "twenty million, five hundred six thousand, four hundred five".