661584778 has 4 divisors (see below), whose sum is σ = 992377170. Its totient is φ = 330792388.

The previous prime is 661584761. The next prime is 661584797. The reversal of 661584778 is 877485166.

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

It can be written as a sum of positive squares in only one way, i.e., 661158369 + 426409 = 25713^2 + 653^2 .

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 165396193 + ... + 165396196.

Almost surely, 2^661584778 is an apocalyptic number.

661584778 is a deficient number, since it is larger than the sum of its proper divisors (330792392).

661584778 is a wasteful number, since it uses less digits than its factorization.

661584778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330792391.

The product of its digits is 2257920, while the sum is 52.

The square root of 661584778 is about 25721.2903642100. The cubic root of 661584778 is about 871.3550812137.

The spelling of 661584778 in words is "six hundred sixty-one million, five hundred eighty-four thousand, seven hundred seventy-eight".