661191009 has 8 divisors (see below), whose sum is σ = 886459392. Its totient is φ = 438358320.

The previous prime is 661191007. The next prime is 661191023. The reversal of 661191009 is 900191166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661191009 - 2¹ = 661191007 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661191007) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 608289 + ... + 609374.

It is an arithmetic number, because the mean of its divisors is an integer number (110807424).

Almost surely, 2^661191009 is an apocalyptic number.

It is an amenable number.

661191009 is a deficient number, since it is larger than the sum of its proper divisors (225268383).

661191009 is a wasteful number, since it uses less digits than its factorization.

661191009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1217847.

The product of its (nonzero) digits is 2916, while the sum is 33.

The square root of 661191009 is about 25713.6346905683. The cubic root of 661191009 is about 871.1821728048.

The spelling of 661191009 in words is "six hundred sixty-one million, one hundred ninety-one thousand, nine".