20997181 has 2 divisors, whose sum is σ = 20997182. Its totient is φ = 20997180.

The previous prime is 20997149. The next prime is 20997187. The reversal of 20997181 is 18179902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20169081 + 828100 = 4491^2 + 910^2 .

It is a cyclic number.

It is not a de Polignac number, because 20997181 - 2⁵ = 20997149 is a prime.

It is a super-2 number, since 2×20997181² = 881763219893522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20997181.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20997187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10498590 + 10498591.

It is an arithmetic number, because the mean of its divisors is an integer number (10498591).

Almost surely, 2^20997181 is an apocalyptic number.

It is an amenable number.

20997181 is a deficient number, since it is larger than the sum of its proper divisors (1).

20997181 is an equidigital number, since it uses as much as digits as its factorization.

20997181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 20997181 is about 4582.2681065167. The cubic root of 20997181 is about 275.8800719948.

The spelling of 20997181 in words is "twenty million, nine hundred ninety-seven thousand, one hundred eighty-one".