1661356081 has 16 divisors (see below), whose sum is σ = 2072292480. Its totient is φ = 1293943680.

The previous prime is 1661356069. The next prime is 1661356097. The reversal of 1661356081 is 1806531661.

It is a cyclic number.

It is not a de Polignac number, because 1661356081 - 2⁵ = 1661356049 is a prime.

It is a super-2 number, since 2×1661356081² = 5520208055751357122, which contains 22 as substring.

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 1661356081.

It is not an unprimeable number, because it can be changed into a prime (1661356481) 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 15 ways as a sum of consecutive naturals, for example, 220285 + ... + 227701.

It is an arithmetic number, because the mean of its divisors is an integer number (129518280).

Almost surely, 2^1661356081 is an apocalyptic number.

1661356081 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1661356081 is a deficient number, since it is larger than the sum of its proper divisors (410936399).

1661356081 is a wasteful number, since it uses less digits than its factorization.

1661356081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10344.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 1661356081 is about 40759.7360271138. The cubic root of 1661356081 is about 1184.3704825154.

The spelling of 1661356081 in words is "one billion, six hundred sixty-one million, three hundred fifty-six thousand, eighty-one".