861809645 has 8 divisors (see below), whose sum is σ = 1095005304. Its totient is φ = 648891904.

The previous prime is 861809623. The next prime is 861809651. The reversal of 861809645 is 546908168.

It can be written as a sum of positive squares in 4 ways, for example, as 259499881 + 602309764 = 16109^2 + 24542^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 861809645 - 2¹⁰ = 861808621 is a prime.

It is a super-3 number, since 3×861809645³ (a number of 28 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 861809645.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5069384 + ... + 5069553.

It is an arithmetic number, because the mean of its divisors is an integer number (136875663).

Almost surely, 2^861809645 is an apocalyptic number.

861809645 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

861809645 is a deficient number, since it is larger than the sum of its proper divisors (233195659).

861809645 is a wasteful number, since it uses less digits than its factorization.

861809645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10138959.

The product of its (nonzero) digits is 414720, while the sum is 47.

The square root of 861809645 is about 29356.5945743031. The cubic root of 861809645 is about 951.6350954930.

The spelling of 861809645 in words is "eight hundred sixty-one million, eight hundred nine thousand, six hundred forty-five".