1611663661 has 4 divisors (see below), whose sum is σ = 1667238300. Its totient is φ = 1556089024.

The previous prime is 1611663653. The next prime is 1611663667. The reversal of 1611663661 is 1663661161.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1055600100 + 556063561 = 32490^2 + 23581^2 .

It is a cyclic number.

It is not a de Polignac number, because 1611663661 - 2³ = 1611663653 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1611663661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1611663667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27787276 + ... + 27787333.

It is an arithmetic number, because the mean of its divisors is an integer number (416809575).

Almost surely, 2^1611663661 is an apocalyptic number.

It is an amenable number.

1611663661 is a deficient number, since it is larger than the sum of its proper divisors (55574639).

1611663661 is an equidigital number, since it uses as much as digits as its factorization.

1611663661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55574638.

The product of its digits is 23328, while the sum is 37.

The square root of 1611663661 is about 40145.5310215222. The cubic root of 1611663661 is about 1172.4422797450.

The spelling of 1611663661 in words is "one billion, six hundred eleven million, six hundred sixty-three thousand, six hundred sixty-one".