20647945 has 16 divisors (see below), whose sum is σ = 26342928. Its totient is φ = 15482880.

The previous prime is 20647943. The next prime is 20647967. The reversal of 20647945 is 54974602.

It can be written as a sum of positive squares in 8 ways, for example, as 99856 + 20548089 = 316^2 + 4533^2 .

It is not a de Polignac number, because 20647945 - 2¹ = 20647943 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20647943) 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, 35497 + ... + 36073.

It is an arithmetic number, because the mean of its divisors is an integer number (1646433).

Almost surely, 2^20647945 is an apocalyptic number.

It is an amenable number.

20647945 is a deficient number, since it is larger than the sum of its proper divisors (5694983).

20647945 is a wasteful number, since it uses less digits than its factorization.

20647945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1020.

The product of its (nonzero) digits is 60480, while the sum is 37.

The square root of 20647945 is about 4544.0009903168. Note that the first 3 decimals coincide. The cubic root of 20647945 is about 274.3419860029.

The spelling of 20647945 in words is "twenty million, six hundred forty-seven thousand, nine hundred forty-five".