20506905 has 16 divisors (see below), whose sum is σ = 36456960. Its totient is φ = 10936944.

The previous prime is 20506897. The next prime is 20506921. The reversal of 20506905 is 50960502.

It is not a de Polignac number, because 20506905 - 2³ = 20506897 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 75817 + ... + 76086.

It is an arithmetic number, because the mean of its divisors is an integer number (2278560).

Almost surely, 2^20506905 is an apocalyptic number.

It is an amenable number.

20506905 is a deficient number, since it is larger than the sum of its proper divisors (15950055).

20506905 is a wasteful number, since it uses less digits than its factorization.

20506905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151917 (or 151911 counting only the distinct ones).

The product of its (nonzero) digits is 2700, while the sum is 27.

The square root of 20506905 is about 4528.4550345565. The cubic root of 20506905 is about 273.7159086839.

The spelling of 20506905 in words is "twenty million, five hundred six thousand, nine hundred five".