861691001 has 4 divisors (see below), whose sum is σ = 861780900. Its totient is φ = 861601104.

The previous prime is 861690971. The next prime is 861691027. The reversal of 861691001 is 100196168.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 469848976 + 391842025 = 21676^2 + 19795^2 .

It is a cyclic number.

It is not a de Polignac number, because 861691001 - 2⁶ = 861690937 is a prime.

It is a super-2 number, since 2×861691001² = 1485022762408764002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861691031) 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 3 ways as a sum of consecutive naturals, for example, 28586 + ... + 50403.

It is an arithmetic number, because the mean of its divisors is an integer number (215445225).

Almost surely, 2^861691001 is an apocalyptic number.

It is an amenable number.

861691001 is a deficient number, since it is larger than the sum of its proper divisors (89899).

861691001 is a wasteful number, since it uses less digits than its factorization.

861691001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89898.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 861691001 is about 29354.5737662804. The cubic root of 861691001 is about 951.5914234453.

The spelling of 861691001 in words is "eight hundred sixty-one million, six hundred ninety-one thousand, one".