1999966661 has 32 divisors (see below), whose sum is σ = 2587613952. Its totient is φ = 1500456960.

The previous prime is 1999966621. The next prime is 1999966681. The reversal of 1999966661 is 1666699991.

It is a cyclic number.

It is not a de Polignac number, because 1999966661 - 2²² = 1995772357 is a prime.

It is a super-2 number, since 2×1999966661² = 7999733290222977842, which contains 22 as substring.

1999966661 is a strobogrammatic number because it is the same when read upside-down.

It is a junction number, because it is equal to n+sod(n) for n = 1999966594 and 1999966603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1999966621) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 272735 + ... + 279971.

It is an arithmetic number, because the mean of its divisors is an integer number (80862936).

Almost surely, 2^1999966661 is an apocalyptic number.

1999966661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1999966661 is a deficient number, since it is larger than the sum of its proper divisors (587647291).

1999966661 is a wasteful number, since it uses less digits than its factorization.

1999966661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7389.

The product of its digits is 8503056, while the sum is 62.

The square root of 1999966661 is about 44720.9868070909. The cubic root of 1999966661 is about 1259.9140491047.

The spelling of 1999966661 in words is "one billion, nine hundred ninety-nine million, nine hundred sixty-six thousand, six hundred sixty-one".