20505155 has 32 divisors (see below), whose sum is σ = 27993600. Its totient is φ = 14291200.

The previous prime is 20505151. The next prime is 20505157. The reversal of 20505155 is 55150502.

It is not a de Polignac number, because 20505155 - 2² = 20505151 is a prime.

It is a super-2 number, since 2×20505155² = 840922763148050, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20505155.

It is not an unprimeable number, because it can be changed into a prime (20505151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 230351 + ... + 230439.

It is an arithmetic number, because the mean of its divisors is an integer number (874800).

Almost surely, 2^20505155 is an apocalyptic number.

20505155 is a deficient number, since it is larger than the sum of its proper divisors (7488445).

20505155 is a wasteful number, since it uses less digits than its factorization.

20505155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 235.

The product of its (nonzero) digits is 1250, while the sum is 23.

The square root of 20505155 is about 4528.2618078022. The cubic root of 20505155 is about 273.7081224209.

Adding to 20505155 its reverse (55150502), we get a palindrome (75655657).

The spelling of 20505155 in words is "twenty million, five hundred five thousand, one hundred fifty-five".