20045781 has 24 divisors (see below), whose sum is σ = 33658560. Its totient is φ = 11258496.

The previous prime is 20045777. The next prime is 20045789. The reversal of 20045781 is 18754002.

20045781 is a `hidden beast` number, since 200 + 457 + 8 + 1 = 666.

It is not a de Polignac number, because 20045781 - 2² = 20045777 is a prime.

It is a super-2 number, since 2×20045781² = 803666671799922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20045789) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1021 + ... + 6413.

It is an arithmetic number, because the mean of its divisors is an integer number (1402440).

Almost surely, 2^20045781 is an apocalyptic number.

20045781 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20045781 is a deficient number, since it is larger than the sum of its proper divisors (13612779).

20045781 is a wasteful number, since it uses less digits than its factorization.

20045781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5465 (or 5462 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 20045781 is about 4477.2515006419. The cubic root of 20045781 is about 271.6487184164.

Adding to 20045781 its reverse (18754002), we get a palindrome (38799783).

The spelling of 20045781 in words is "twenty million, forty-five thousand, seven hundred eighty-one".