20990171 has 4 divisors (see below), whose sum is σ = 21714000. Its totient is φ = 20266344.

The previous prime is 20990143. The next prime is 20990183. The reversal of 20990171 is 17109902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17109902 = 2 ⋅8554951.

It is a cyclic number.

It is not a de Polignac number, because 20990171 - 2¹⁰ = 20989147 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 723799 = 20990171 / (2 + 0 + 9 + 9 + 0 + 1 + 7 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20990111) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 361871 + ... + 361928.

It is an arithmetic number, because the mean of its divisors is an integer number (5428500).

Almost surely, 2^20990171 is an apocalyptic number.

20990171 is a deficient number, since it is larger than the sum of its proper divisors (723829).

20990171 is an equidigital number, since it uses as much as digits as its factorization.

20990171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 723828.

The product of its (nonzero) digits is 1134, while the sum is 29.

The square root of 20990171 is about 4581.5031376176. The cubic root of 20990171 is about 275.8493673245.

The spelling of 20990171 in words is "twenty million, nine hundred ninety thousand, one hundred seventy-one".