1661540644 has 27 divisors (see below), whose sum is σ = 2953631667. Its totient is φ = 817848768.

The previous prime is 1661540641. The next prime is 1661540653. The reversal of 1661540644 is 4460451661.

The square root of 1661540644 is 40762.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 58339044 + 1603201600 = 7638^2 + 40040^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661540641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 7255522 + ... + 7255750.

Almost surely, 2^1661540644 is an apocalyptic number.

1661540644 is the 40762-nd square number.

It is an amenable number.

1661540644 is a deficient number, since it is larger than the sum of its proper divisors (1292091023).

1661540644 is an frugal number, since it uses more digits than its factorization.

1661540644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 640 (or 320 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 37.

The cubic root of 1661540644 is about 1184.4143388321.

The spelling of 1661540644 in words is "one billion, six hundred sixty-one million, five hundred forty thousand, six hundred forty-four".