2128197661 has 4 divisors (see below), whose sum is σ = 2129665824. Its totient is φ = 2126729500.

The previous prime is 2128197653. The next prime is 2128197691. The reversal of 2128197661 is 1667918212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2128197661 - 2³ = 2128197653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2128197611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 731905 + ... + 734806.

It is an arithmetic number, because the mean of its divisors is an integer number (532416456).

Almost surely, 2^2128197661 is an apocalyptic number.

It is an amenable number.

2128197661 is a deficient number, since it is larger than the sum of its proper divisors (1468163).

2128197661 is a wasteful number, since it uses less digits than its factorization.

2128197661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1468162.

The product of its digits is 72576, while the sum is 43.

The square root of 2128197661 is about 46132.3927517314. The cubic root of 2128197661 is about 1286.2853416945.

The spelling of 2128197661 in words is "two billion, one hundred twenty-eight million, one hundred ninety-seven thousand, six hundred sixty-one".