1645378381 has 2 divisors, whose sum is σ = 1645378382. Its totient is φ = 1645378380.

The previous prime is 1645378363. The next prime is 1645378387. The reversal of 1645378381 is 1838735461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1085109481 + 560268900 = 32941^2 + 23670^2 .

It is a cyclic number.

It is not a de Polignac number, because 1645378381 - 2⁵ = 1645378349 is a prime.

It is a super-2 number, since 2×1645378381² = 5414540033324362322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1645378387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 822689190 + 822689191.

It is an arithmetic number, because the mean of its divisors is an integer number (822689191).

Almost surely, 2^1645378381 is an apocalyptic number.

It is an amenable number.

1645378381 is a deficient number, since it is larger than the sum of its proper divisors (1).

1645378381 is an equidigital number, since it uses as much as digits as its factorization.

1645378381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 483840, while the sum is 46.

The square root of 1645378381 is about 40563.2639342546. The cubic root of 1645378381 is about 1180.5614442558.

The spelling of 1645378381 in words is "one billion, six hundred forty-five million, three hundred seventy-eight thousand, three hundred eighty-one".