20506157 has 6 divisors (see below), whose sum is σ = 23854158. Its totient is φ = 17576664.

The previous prime is 20506153. The next prime is 20506163. The reversal of 20506157 is 75160502.

It can be written as a sum of positive squares in only one way, i.e., 19945156 + 561001 = 4466^2 + 749^2 .

It is not a de Polignac number, because 20506157 - 2² = 20506153 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20506151) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 209198 + ... + 209295.

It is an arithmetic number, because the mean of its divisors is an integer number (3975693).

Almost surely, 2^20506157 is an apocalyptic number.

It is an amenable number.

20506157 is a deficient number, since it is larger than the sum of its proper divisors (3348001).

20506157 is an equidigital number, since it uses as much as digits as its factorization.

20506157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 418507 (or 418500 counting only the distinct ones).

The product of its (nonzero) digits is 2100, while the sum is 26.

The square root of 20506157 is about 4528.3724449299. The cubic root of 20506157 is about 273.7125806668.

Adding to 20506157 its reverse (75160502), we get a palindrome (95666659).

The spelling of 20506157 in words is "twenty million, five hundred six thousand, one hundred fifty-seven".