18972209 has 4 divisors (see below), whose sum is σ = 18997104. Its totient is φ = 18947316.

The previous prime is 18972199. The next prime is 18972229. The reversal of 18972209 is 90227981.

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: 90227981 = 347 ⋅260023.

It is a cyclic number.

It is not a de Polignac number, because 18972209 - 2⁴ = 18972193 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18972229) 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, 11267 + ... + 12840.

It is an arithmetic number, because the mean of its divisors is an integer number (4749276).

Almost surely, 2^18972209 is an apocalyptic number.

It is an amenable number.

18972209 is a deficient number, since it is larger than the sum of its proper divisors (24895).

18972209 is an equidigital number, since it uses as much as digits as its factorization.

18972209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24894.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 18972209 is about 4355.7099306542. The cubic root of 18972209 is about 266.7100004231.

The spelling of 18972209 in words is "eighteen million, nine hundred seventy-two thousand, two hundred nine".