18969221 has 2 divisors, whose sum is σ = 18969222. Its totient is φ = 18969220.

The previous prime is 18969169. The next prime is 18969233. The reversal of 18969221 is 12296981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11296321 + 7672900 = 3361^2 + 2770^2 .

It is a cyclic number.

It is not a de Polignac number, because 18969221 - 2¹⁰ = 18968197 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18969421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9484610 + 9484611.

It is an arithmetic number, because the mean of its divisors is an integer number (9484611).

Almost surely, 2^18969221 is an apocalyptic number.

It is an amenable number.

18969221 is a deficient number, since it is larger than the sum of its proper divisors (1).

18969221 is an equidigital number, since it uses as much as digits as its factorization.

18969221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 38.

The square root of 18969221 is about 4355.3669191011. The cubic root of 18969221 is about 266.6959979889.

The spelling of 18969221 in words is "eighteen million, nine hundred sixty-nine thousand, two hundred twenty-one".