18797221 has 4 divisors (see below), whose sum is σ = 19305292. Its totient is φ = 18289152.

The previous prime is 18797209. The next prime is 18797239. The reversal of 18797221 is 12279781.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17969121 + 828100 = 4239^2 + 910^2 .

It is a cyclic number.

It is not a de Polignac number, because 18797221 - 2⁹ = 18796709 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 508033 = 18797221 / (1 + 8 + 7 + 9 + 7 + 2 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18797201) 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 3 ways as a sum of consecutive naturals, for example, 253980 + ... + 254053.

It is an arithmetic number, because the mean of its divisors is an integer number (4826323).

Almost surely, 2^18797221 is an apocalyptic number.

It is an amenable number.

18797221 is a deficient number, since it is larger than the sum of its proper divisors (508071).

18797221 is an equidigital number, since it uses as much as digits as its factorization.

18797221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 508070.

The product of its digits is 14112, while the sum is 37.

The square root of 18797221 is about 4335.5762016138. The cubic root of 18797221 is about 265.8874766689.

The spelling of 18797221 in words is "eighteen million, seven hundred ninety-seven thousand, two hundred twenty-one".