66638821706 has 4 divisors (see below), whose sum is σ = 99958232562. Its totient is φ = 33319410852.

The previous prime is 66638821631. The next prime is 66638821721. The reversal of 66638821706 is 60712883666.

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., 33983079025 + 32655742681 = 184345^2 + 180709^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16659705425 + ... + 16659705428.

Almost surely, 2^66638821706 is an apocalyptic number.

66638821706 is a deficient number, since it is larger than the sum of its proper divisors (33319410856).

66638821706 is a wasteful number, since it uses less digits than its factorization.

66638821706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33319410855.

The product of its (nonzero) digits is 3483648, while the sum is 53.

The spelling of 66638821706 in words is "sixty-six billion, six hundred thirty-eight million, eight hundred twenty-one thousand, seven hundred six".