861491 has 2 divisors, whose sum is σ = 861492. Its totient is φ = 861490.

The previous prime is 861439. The next prime is 861493. The reversal of 861491 is 194168.

861491 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-861491 is a prime.

It is a Sophie Germain prime.

Together with 861493, it forms a pair of twin primes.

It is a Chen prime.

It is a plaindrome in base 12.

It is not a weakly prime, because it can be changed into another prime (861493) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430745 + 430746.

It is an arithmetic number, because the mean of its divisors is an integer number (430746).

2⁸⁶¹⁴⁹¹ is an apocalyptic number.

861491 is a deficient number, since it is larger than the sum of its proper divisors (1).

861491 is an equidigital number, since it uses as much as digits as its factorization.

861491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 29.

The square root of 861491 is about 928.1653947438. The cubic root of 861491 is about 95.1517795365.

The spelling of 861491 in words is "eight hundred sixty-one thousand, four hundred ninety-one".