1664441381 has 2 divisors, whose sum is σ = 1664441382. Its totient is φ = 1664441380.

The previous prime is 1664441369. The next prime is 1664441417. The reversal of 1664441381 is 1831444661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1612745281 + 51696100 = 40159^2 + 7190^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1664441381 is a prime.

It is a super-3 number, since 3×1664441381³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1664441281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 832220690 + 832220691.

It is an arithmetic number, because the mean of its divisors is an integer number (832220691).

Almost surely, 2^1664441381 is an apocalyptic number.

It is an amenable number.

1664441381 is a deficient number, since it is larger than the sum of its proper divisors (1).

1664441381 is an equidigital number, since it uses as much as digits as its factorization.

1664441381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 55296, while the sum is 38.

The square root of 1664441381 is about 40797.5658710174. The cubic root of 1664441381 is about 1185.1031928982.

The spelling of 1664441381 in words is "one billion, six hundred sixty-four million, four hundred forty-one thousand, three hundred eighty-one".