1645378331 has 4 divisors (see below), whose sum is σ = 1645604064. Its totient is φ = 1645152600.

The previous prime is 1645378297. The next prime is 1645378349. The reversal of 1645378331 is 1338735461.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1645378331 - 2²⁶ = 1578269467 is a prime.

It is a super-2 number, since 2×1645378331² = 5414539704248691122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1645378381) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 101555 + ... + 116636.

It is an arithmetic number, because the mean of its divisors is an integer number (411401016).

Almost surely, 2^1645378331 is an apocalyptic number.

1645378331 is a deficient number, since it is larger than the sum of its proper divisors (225733).

1645378331 is an equidigital number, since it uses as much as digits as its factorization.

1645378331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 225732.

The product of its digits is 181440, while the sum is 41.

The square root of 1645378331 is about 40563.2633179334. The cubic root of 1645378331 is about 1180.5614322975.

The spelling of 1645378331 in words is "one billion, six hundred forty-five million, three hundred seventy-eight thousand, three hundred thirty-one".