20505789 has 6 divisors (see below), whose sum is σ = 29619486. Its totient is φ = 13670520.

The previous prime is 20505761. The next prime is 20505799. The reversal of 20505789 is 98750502.

It can be written as a sum of positive squares in only one way, i.e., 19873764 + 632025 = 4458^2 + 795^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20505789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20505799) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1139202 + ... + 1139219.

It is an arithmetic number, because the mean of its divisors is an integer number (4936581).

Almost surely, 2^20505789 is an apocalyptic number.

It is an amenable number.

20505789 is a deficient number, since it is larger than the sum of its proper divisors (9113697).

20505789 is a wasteful number, since it uses less digits than its factorization.

20505789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2278427 (or 2278424 counting only the distinct ones).

The product of its (nonzero) digits is 25200, while the sum is 36.

The square root of 20505789 is about 4528.3318120473. The cubic root of 20505789 is about 273.7109433239.

The spelling of 20505789 in words is "twenty million, five hundred five thousand, seven hundred eighty-nine".