1820666381 has 2 divisors, whose sum is σ = 1820666382. Its totient is φ = 1820666380.

The previous prime is 1820666369. The next prime is 1820666387. The reversal of 1820666381 is 1836660281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1761145156 + 59521225 = 41966^2 + 7715^2 .

It is an emirp because it is prime and its reverse (1836660281) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1820666381 is a prime.

It is a super-2 number, since 2×1820666381² = 6629652141807274322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1820666387) 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 as a sum of consecutive naturals, namely, 910333190 + 910333191.

It is an arithmetic number, because the mean of its divisors is an integer number (910333191).

Almost surely, 2^1820666381 is an apocalyptic number.

It is an amenable number.

1820666381 is a deficient number, since it is larger than the sum of its proper divisors (1).

1820666381 is an equidigital number, since it uses as much as digits as its factorization.

1820666381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 82944, while the sum is 41.

The square root of 1820666381 is about 42669.2674064132. The cubic root of 1820666381 is about 1221.0781432833.

The spelling of 1820666381 in words is "one billion, eight hundred twenty million, six hundred sixty-six thousand, three hundred eighty-one".