18771221 has 16 divisors (see below), whose sum is σ = 22800000. Its totient is φ = 15095808.

The previous prime is 18771209. The next prime is 18771223. The reversal of 18771221 is 12217781.

It is not a de Polignac number, because 18771221 - 2⁶ = 18771157 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18771223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14405 + ... + 15653.

It is an arithmetic number, because the mean of its divisors is an integer number (1425000).

Almost surely, 2^18771221 is an apocalyptic number.

It is an amenable number.

18771221 is a deficient number, since it is larger than the sum of its proper divisors (4028779).

18771221 is a wasteful number, since it uses less digits than its factorization.

18771221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1388.

The product of its digits is 1568, while the sum is 29.

The square root of 18771221 is about 4332.5767159971. The cubic root of 18771221 is about 265.7648297415.

The spelling of 18771221 in words is "eighteen million, seven hundred seventy-one thousand, two hundred twenty-one".