6661688378 has 4 divisors (see below), whose sum is σ = 9992532570. Its totient is φ = 3330844188.

The previous prime is 6661688309. The next prime is 6661688399. The reversal of 6661688378 is 8738861666.

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., 4498787329 + 2162901049 = 67073^2 + 46507^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1665422093 + ... + 1665422096.

Almost surely, 2^6661688378 is an apocalyptic number.

6661688378 is a deficient number, since it is larger than the sum of its proper divisors (3330844192).

6661688378 is a wasteful number, since it uses less digits than its factorization.

6661688378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3330844191.

The product of its digits is 13934592, while the sum is 59.

The square root of 6661688378 is about 81619.1667318406. The cubic root of 6661688378 is about 1881.6034662037.

The spelling of 6661688378 in words is "six billion, six hundred sixty-one million, six hundred eighty-eight thousand, three hundred seventy-eight".