20917145 has 4 divisors (see below), whose sum is σ = 25100580. Its totient is φ = 16733712.

The previous prime is 20917133. The next prime is 20917153. The reversal of 20917145 is 54171902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54171902 = 2 ⋅27085951.

It can be written as a sum of positive squares in 2 ways, for example, as 6869641 + 14047504 = 2621^2 + 3748^2 .

It is a cyclic number.

It is not a de Polignac number, because 20917145 - 2⁴ = 20917129 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2091710 + ... + 2091719.

It is an arithmetic number, because the mean of its divisors is an integer number (6275145).

Almost surely, 2^20917145 is an apocalyptic number.

It is an amenable number.

20917145 is a deficient number, since it is larger than the sum of its proper divisors (4183435).

20917145 is an equidigital number, since it uses as much as digits as its factorization.

20917145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4183434.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 20917145 is about 4573.5265386789. The cubic root of 20917145 is about 275.5290970725.

The spelling of 20917145 in words is "twenty million, nine hundred seventeen thousand, one hundred forty-five".