20781705 has 16 divisors (see below), whose sum is σ = 38001024. Its totient is φ = 9500160.

The previous prime is 20781703. The next prime is 20781731. The reversal of 20781705 is 50718702.

It is a happy number.

It is not a de Polignac number, because 20781705 - 2¹ = 20781703 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20781703) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 98856 + ... + 99065.

It is an arithmetic number, because the mean of its divisors is an integer number (2375064).

Almost surely, 2^20781705 is an apocalyptic number.

It is an amenable number.

20781705 is a deficient number, since it is larger than the sum of its proper divisors (17219319).

20781705 is a wasteful number, since it uses less digits than its factorization.

20781705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197936.

The product of its (nonzero) digits is 3920, while the sum is 30.

The square root of 20781705 is about 4558.6955371027. The cubic root of 20781705 is about 274.9331187217.

The spelling of 20781705 in words is "twenty million, seven hundred eighty-one thousand, seven hundred five".