661647172 has 12 divisors (see below), whose sum is σ = 1189176940. Its totient is φ = 321882336.

The previous prime is 661647143. The next prime is 661647179. The reversal of 661647172 is 271746166.

It can be written as a sum of positive squares in 2 ways, for example, as 562923076 + 98724096 = 23726^2 + 9936^2 .

It is not an unprimeable number, because it can be changed into a prime (661647179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2235147 + ... + 2235442.

Almost surely, 2^661647172 is an apocalyptic number.

It is an amenable number.

661647172 is a deficient number, since it is larger than the sum of its proper divisors (527529768).

661647172 is a wasteful number, since it uses less digits than its factorization.

661647172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4470630 (or 4470628 counting only the distinct ones).

The product of its digits is 84672, while the sum is 40.

The square root of 661647172 is about 25722.5032218873. The cubic root of 661647172 is about 871.3824728254.

The spelling of 661647172 in words is "six hundred sixty-one million, six hundred forty-seven thousand, one hundred seventy-two".