861091779 has 16 divisors (see below), whose sum is σ = 1199153664. Its totient is φ = 548592000.

The previous prime is 861091771. The next prime is 861091789. The reversal of 861091779 is 977190168.

It is a happy number.

It is not a de Polignac number, because 861091779 - 2³ = 861091771 is a prime.

It is a super-2 number, since 2×861091779² = 1482958103722769682, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (861091771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 77674 + ... + 88064.

It is an arithmetic number, because the mean of its divisors is an integer number (74947104).

Almost surely, 2^861091779 is an apocalyptic number.

861091779 is a deficient number, since it is larger than the sum of its proper divisors (338061885).

861091779 is a wasteful number, since it uses less digits than its factorization.

861091779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11618.

The product of its (nonzero) digits is 190512, while the sum is 48.

The square root of 861091779 is about 29344.3653705443. The cubic root of 861091779 is about 951.3707926381.

The spelling of 861091779 in words is "eight hundred sixty-one million, ninety-one thousand, seven hundred seventy-nine".