1812661221 has 32 divisors (see below), whose sum is σ = 2800189440. Its totient is φ = 1021640256.

The previous prime is 1812661217. The next prime is 1812661231. The reversal of 1812661221 is 1221662181.

It is not a de Polignac number, because 1812661221 - 2² = 1812661217 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1812661231) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 475495 + ... + 479291.

It is an arithmetic number, because the mean of its divisors is an integer number (87505920).

Almost surely, 2^1812661221 is an apocalyptic number.

It is an amenable number.

1812661221 is a deficient number, since it is larger than the sum of its proper divisors (987528219).

1812661221 is a wasteful number, since it uses less digits than its factorization.

1812661221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4113.

The product of its digits is 2304, while the sum is 30.

The square root of 1812661221 is about 42575.3593173328. The cubic root of 1812661221 is about 1219.2858897551.

The spelling of 1812661221 in words is "one billion, eight hundred twelve million, six hundred sixty-one thousand, two hundred twenty-one".