820220666 has 4 divisors (see below), whose sum is σ = 1230331002. Its totient is φ = 410110332.

The previous prime is 820220629. The next prime is 820220677. The reversal of 820220666 is 666022028.

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., 714439441 + 105781225 = 26729^2 + 10285^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 205055165 + ... + 205055168.

Almost surely, 2^820220666 is an apocalyptic number.

820220666 is a deficient number, since it is larger than the sum of its proper divisors (410110336).

820220666 is a wasteful number, since it uses less digits than its factorization.

820220666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410110335.

The product of its (nonzero) digits is 13824, while the sum is 32.

The square root of 820220666 is about 28639.4948628638. The cubic root of 820220666 is about 936.0741146234.

The spelling of 820220666 in words is "eight hundred twenty million, two hundred twenty thousand, six hundred sixty-six".