661631206 has 4 divisors (see below), whose sum is σ = 992446812. Its totient is φ = 330815602.

The previous prime is 661631203. The next prime is 661631207. The reversal of 661631206 is 602136166.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661631203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165407800 + ... + 165407803.

It is an arithmetic number, because the mean of its divisors is an integer number (248111703).

Almost surely, 2^661631206 is an apocalyptic number.

661631206 is a deficient number, since it is larger than the sum of its proper divisors (330815606).

661631206 is a wasteful number, since it uses less digits than its factorization.

661631206 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330815605.

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 661631206 is about 25722.1928691937. The cubic root of 661631206 is about 871.3754637501.

The spelling of 661631206 in words is "six hundred sixty-one million, six hundred thirty-one thousand, two hundred six".