661432217 has 4 divisors (see below), whose sum is σ = 661483956. Its totient is φ = 661380480.

The previous prime is 661432201. The next prime is 661432223. The reversal of 661432217 is 712234166.

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 222278281 + 439153936 = 14909^2 + 20956^2 .

It is a cyclic number.

It is not a de Polignac number, because 661432217 - 2⁴ = 661432201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661432297) 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, 8753 + ... + 37409.

It is an arithmetic number, because the mean of its divisors is an integer number (165370989).

Almost surely, 2^661432217 is an apocalyptic number.

It is an amenable number.

661432217 is a deficient number, since it is larger than the sum of its proper divisors (51739).

661432217 is a wasteful number, since it uses less digits than its factorization.

661432217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51738.

The product of its digits is 12096, while the sum is 32.

The square root of 661432217 is about 25718.3245371855. The cubic root of 661432217 is about 871.2880981016.

The spelling of 661432217 in words is "six hundred sixty-one million, four hundred thirty-two thousand, two hundred seventeen".