1661517661 has 8 divisors (see below), whose sum is σ = 1802163384. Its totient is φ = 1525639680.

The previous prime is 1661517623. The next prime is 1661517679. The reversal of 1661517661 is 1667151661.

It can be written as a sum of positive squares in 4 ways, for example, as 213715161 + 1447802500 = 14619^2 + 38050^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1661517661 - 2¹¹ = 1661515613 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 (1661517161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1191210 + ... + 1192603.

It is an arithmetic number, because the mean of its divisors is an integer number (225270423).

Almost surely, 2^1661517661 is an apocalyptic number.

It is an amenable number.

1661517661 is a deficient number, since it is larger than the sum of its proper divisors (140645723).

1661517661 is a wasteful number, since it uses less digits than its factorization.

1661517661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2383871.

The product of its digits is 45360, while the sum is 40.

The square root of 1661517661 is about 40761.7180820436. The cubic root of 1661517661 is about 1184.4088777318.

The spelling of 1661517661 in words is "one billion, six hundred sixty-one million, five hundred seventeen thousand, six hundred sixty-one".