18220261 has 4 divisors (see below), whose sum is σ = 18644032. Its totient is φ = 17796492.

The previous prime is 18220247. The next prime is 18220271. The reversal of 18220261 is 16202281.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16202281 = 23 ⋅704447.

It is a cyclic number.

It is not a de Polignac number, because 18220261 - 2¹³ = 18212069 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18220271) 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, 211821 + ... + 211906.

It is an arithmetic number, because the mean of its divisors is an integer number (4661008).

Almost surely, 2^18220261 is an apocalyptic number.

It is an amenable number.

18220261 is a deficient number, since it is larger than the sum of its proper divisors (423771).

18220261 is an equidigital number, since it uses as much as digits as its factorization.

18220261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 423770.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 18220261 is about 4268.5197668513. The cubic root of 18220261 is about 263.1387847169.

It can be divided in two parts, 18220 and 261, that added together give a palindrome (18481).

The spelling of 18220261 in words is "eighteen million, two hundred twenty thousand, two hundred sixty-one".