1990000661 has 4 divisors (see below), whose sum is σ = 2170909824. Its totient is φ = 1809091500.

The previous prime is 1990000643. The next prime is 1990000669. The reversal of 1990000661 is 1660000991.

It is a happy number.

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 1990000661 - 2²⁶ = 1922891797 is a prime.

1990000661 is a strobogrammatic number because it is the same when read upside-down.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1990000669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 90454565 + ... + 90454586.

It is an arithmetic number, because the mean of its divisors is an integer number (542727456).

Almost surely, 2^1990000661 is an apocalyptic number.

1990000661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1990000661 is a deficient number, since it is larger than the sum of its proper divisors (180909163).

1990000661 is a wasteful number, since it uses less digits than its factorization.

1990000661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180909162.

The product of its (nonzero) digits is 2916, while the sum is 32.

The square root of 1990000661 is about 44609.4234551401. The cubic root of 1990000661 is about 1257.8178112094.

The spelling of 1990000661 in words is "one billion, nine hundred ninety million, six hundred sixty-one", and thus it is an aban number.