1642131661 has 4 divisors (see below), whose sum is σ = 1644162300. Its totient is φ = 1640101024.

The previous prime is 1642131653. The next prime is 1642131671. The reversal of 1642131661 is 1661312461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1661312461 = 191 ⋅8697971.

It can be written as a sum of positive squares in 2 ways, for example, as 1559776036 + 82355625 = 39494^2 + 9075^2 .

It is a cyclic number.

It is not a de Polignac number, because 1642131661 - 2³ = 1642131653 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 (1642131671) 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, 1014106 + ... + 1015723.

It is an arithmetic number, because the mean of its divisors is an integer number (411040575).

Almost surely, 2^1642131661 is an apocalyptic number.

It is an amenable number.

1642131661 is a deficient number, since it is larger than the sum of its proper divisors (2030639).

1642131661 is an equidigital number, since it uses as much as digits as its factorization.

1642131661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2030638.

The product of its digits is 5184, while the sum is 31.

The square root of 1642131661 is about 40523.2237241807. The cubic root of 1642131661 is about 1179.7844241348.

The spelling of 1642131661 in words is "one billion, six hundred forty-two million, one hundred thirty-one thousand, six hundred sixty-one".