1666220001 has 16 divisors (see below), whose sum is σ = 2288492544. Its totient is φ = 1077560064.

The previous prime is 1666219993. The next prime is 1666220009. The reversal of 1666220001 is 1000226661.

It is an interprime number because it is at equal distance from previous prime (1666219993) and next prime (1666220009).

It is not a de Polignac number, because 1666220001 - 2³ = 1666219993 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1666220009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15136 + ... + 59678.

It is an arithmetic number, because the mean of its divisors is an integer number (143030784).

Almost surely, 2^1666220001 is an apocalyptic number.

It is an amenable number.

1666220001 is a deficient number, since it is larger than the sum of its proper divisors (622272543).

1666220001 is a wasteful number, since it uses less digits than its factorization.

1666220001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44920.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 1666220001 is about 40819.3581649687. The cubic root of 1666220001 is about 1185.5251758922.

Adding to 1666220001 its reverse (1000226661), we get a palindrome (2666446662).

It can be divided in two parts, 16662 and 20001, that added together give a palindrome (36663).

The spelling of 1666220001 in words is "one billion, six hundred sixty-six million, two hundred twenty thousand, one".