18690221 has 4 divisors (see below), whose sum is σ = 20389344. Its totient is φ = 16991100.

The previous prime is 18690211. The next prime is 18690223. The reversal of 18690221 is 12209681.

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.

It is a cyclic number.

It is not a de Polignac number, because 18690221 - 2¹⁰ = 18689197 is a prime.

It is a super-2 number, since 2×18690221² = 698648722057682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18690223) 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, 849545 + ... + 849566.

It is an arithmetic number, because the mean of its divisors is an integer number (5097336).

Almost surely, 2^18690221 is an apocalyptic number.

18690221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18690221 is a deficient number, since it is larger than the sum of its proper divisors (1699123).

18690221 is a wasteful number, since it uses less digits than its factorization.

18690221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1699122.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 18690221 is about 4323.2188239783. The cubic root of 18690221 is about 265.3820098668.

The spelling of 18690221 in words is "eighteen million, six hundred ninety thousand, two hundred twenty-one".