1661206505 has 8 divisors (see below), whose sum is σ = 2278226112. Its totient is φ = 1139113008.

The previous prime is 1661206453. The next prime is 1661206531. The reversal of 1661206505 is 5056021661.

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 1661206505 - 2⁸ = 1661206249 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23731487 + ... + 23731556.

It is an arithmetic number, because the mean of its divisors is an integer number (284778264).

Almost surely, 2^1661206505 is an apocalyptic number.

It is an amenable number.

1661206505 is a deficient number, since it is larger than the sum of its proper divisors (617019607).

1661206505 is an equidigital number, since it uses as much as digits as its factorization.

1661206505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47463055.

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 1661206505 is about 40757.9011358534. The cubic root of 1661206505 is about 1184.3349375133.

The spelling of 1661206505 in words is "one billion, six hundred sixty-one million, two hundred six thousand, five hundred five".