1812167221 has 2 divisors, whose sum is σ = 1812167222. Its totient is φ = 1812167220.

The previous prime is 1812167219. The next prime is 1812167249. The reversal of 1812167221 is 1227612181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1765176196 + 46991025 = 42014^2 + 6855^2 .

It is a cyclic number.

It is not a de Polignac number, because 1812167221 - 2¹ = 1812167219 is a prime.

Together with 1812167219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1812167821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 906083610 + 906083611.

It is an arithmetic number, because the mean of its divisors is an integer number (906083611).

Almost surely, 2^1812167221 is an apocalyptic number.

It is an amenable number.

1812167221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1812167221 is an equidigital number, since it uses as much as digits as its factorization.

1812167221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 31.

The square root of 1812167221 is about 42569.5574442582. The cubic root of 1812167221 is about 1219.1751167201.

The spelling of 1812167221 in words is "one billion, eight hundred twelve million, one hundred sixty-seven thousand, two hundred twenty-one".