1661519641 has 4 divisors (see below), whose sum is σ = 1662815952. Its totient is φ = 1660223332.

The previous prime is 1661519623. The next prime is 1661519653. The reversal of 1661519641 is 1469151661.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1469151661 = 2851 ⋅515311.

It is a cyclic number.

It is not a de Polignac number, because 1661519641 - 2²⁹ = 1124648729 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1661519594 and 1661519603.

It is not an unprimeable number, because it can be changed into a prime (1661519621) 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, 646231 + ... + 648796.

It is an arithmetic number, because the mean of its divisors is an integer number (415703988).

Almost surely, 2^1661519641 is an apocalyptic number.

It is an amenable number.

1661519641 is a deficient number, since it is larger than the sum of its proper divisors (1296311).

1661519641 is a wasteful number, since it uses less digits than its factorization.

1661519641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1296310.

The product of its digits is 38880, while the sum is 40.

The square root of 1661519641 is about 40761.7423695308. The cubic root of 1661519641 is about 1184.4093482110.

The spelling of 1661519641 in words is "one billion, six hundred sixty-one million, five hundred nineteen thousand, six hundred forty-one".