861365781 has 12 divisors (see below), whose sum is σ = 1244800908. Its totient is φ = 573964224.

The previous prime is 861365773. The next prime is 861365831. The reversal of 861365781 is 187563168.

It can be written as a sum of positive squares in 2 ways, for example, as 105390756 + 755975025 = 10266^2 + 27495^2 .

It is not a de Polignac number, because 861365781 - 2³ = 861365773 is a prime.

It is a super-2 number, since 2×861365781² = 1483902017355479922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (861365581) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2850 + ... + 41603.

It is an arithmetic number, because the mean of its divisors is an integer number (103733409).

Almost surely, 2^861365781 is an apocalyptic number.

It is an amenable number.

861365781 is a deficient number, since it is larger than the sum of its proper divisors (383435127).

861365781 is a wasteful number, since it uses less digits than its factorization.

861365781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46612 (or 46609 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The square root of 861365781 is about 29349.0337319647. The cubic root of 861365781 is about 951.4716916215.

The spelling of 861365781 in words is "eight hundred sixty-one million, three hundred sixty-five thousand, seven hundred eighty-one".