661307009 has 4 divisors (see below), whose sum is σ = 721425840. Its totient is φ = 601188180.

The previous prime is 661306991. The next prime is 661307029. The reversal of 661307009 is 900703166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661307009 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (661307029) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30059399 + ... + 30059420.

It is an arithmetic number, because the mean of its divisors is an integer number (180356460).

Almost surely, 2^661307009 is an apocalyptic number.

It is an amenable number.

661307009 is a deficient number, since it is larger than the sum of its proper divisors (60118831).

661307009 is a wasteful number, since it uses less digits than its factorization.

661307009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60118830.

The product of its (nonzero) digits is 6804, while the sum is 32.

The square root of 661307009 is about 25715.8902043075. The cubic root of 661307009 is about 871.2331168444.

The spelling of 661307009 in words is "six hundred sixty-one million, three hundred seven thousand, nine".