1661613881 has 6 divisors (see below), whose sum is σ = 1765105710. Its totient is φ = 1563871616.

The previous prime is 1661613853. The next prime is 1661613883. The reversal of 1661613881 is 1883161661.

It can be written as a sum of positive squares in 3 ways, for example, as 426794281 + 1234819600 = 20659^2 + 35140^2 .

It is not a de Polignac number, because 1661613881 - 2³⁰ = 587872057 is a prime.

It is a super-2 number, since 2×1661613881² = 5521921379063764322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661613883) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2874476 + ... + 2875053.

It is an arithmetic number, because the mean of its divisors is an integer number (294184285).

Almost surely, 2^1661613881 is an apocalyptic number.

It is an amenable number.

1661613881 is a deficient number, since it is larger than the sum of its proper divisors (103491829).

1661613881 is an equidigital number, since it uses as much as digits as its factorization.

1661613881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5749563 (or 5749546 counting only the distinct ones).

The product of its digits is 41472, while the sum is 41.

The square root of 1661613881 is about 40762.8983390534. The cubic root of 1661613881 is about 1184.4317406892.

The spelling of 1661613881 in words is "one billion, six hundred sixty-one million, six hundred thirteen thousand, eight hundred eighty-one".