861921791 has 2 divisors, whose sum is σ = 861921792. Its totient is φ = 861921790.

The previous prime is 861921773. The next prime is 861921817. The reversal of 861921791 is 197129168.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 861921791 - 2¹⁸ = 861659647 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (861921761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430960895 + 430960896.

It is an arithmetic number, because the mean of its divisors is an integer number (430960896).

Almost surely, 2^861921791 is an apocalyptic number.

861921791 is a deficient number, since it is larger than the sum of its proper divisors (1).

861921791 is an equidigital number, since it uses as much as digits as its factorization.

861921791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54432, while the sum is 44.

The square root of 861921791 is about 29358.5045770387. The cubic root of 861921791 is about 951.6763719865.

The spelling of 861921791 in words is "eight hundred sixty-one million, nine hundred twenty-one thousand, seven hundred ninety-one".