861258661 has 2 divisors, whose sum is σ = 861258662. Its totient is φ = 861258660.

The previous prime is 861258659. The next prime is 861258683. The reversal of 861258661 is 166852168.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 811908036 + 49350625 = 28494^2 + 7025^2 .

It is a cyclic number.

It is not a de Polignac number, because 861258661 - 2¹ = 861258659 is a prime.

It is a super-2 number, since 2×861258661² = 1483532962295025842, which contains 22 as substring.

Together with 861258659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (861258631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 430629330 + 430629331.

It is an arithmetic number, because the mean of its divisors is an integer number (430629331).

Almost surely, 2^861258661 is an apocalyptic number.

It is an amenable number.

861258661 is a deficient number, since it is larger than the sum of its proper divisors (1).

861258661 is an equidigital number, since it uses as much as digits as its factorization.

861258661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 138240, while the sum is 43.

The square root of 861258661 is about 29347.2087429111. The cubic root of 861258661 is about 951.4322481101.

The spelling of 861258661 in words is "eight hundred sixty-one million, two hundred fifty-eight thousand, six hundred sixty-one".