1661501665 has 8 divisors (see below), whose sum is σ = 1995356520. Its totient is φ = 1328164992.

The previous prime is 1661501663. The next prime is 1661501707. The reversal of 1661501665 is 5661051661.

It can be written as a sum of positive squares in 4 ways, for example, as 76108176 + 1585393489 = 8724^2 + 39817^2 .

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 1661501665 - 2¹ = 1661501663 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1661501663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 122454 + ... + 135343.

It is an arithmetic number, because the mean of its divisors is an integer number (249419565).

Almost surely, 2^1661501665 is an apocalyptic number.

It is an amenable number.

1661501665 is a deficient number, since it is larger than the sum of its proper divisors (333854855).

1661501665 is a wasteful number, since it uses less digits than its factorization.

1661501665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259091.

The product of its (nonzero) digits is 32400, while the sum is 37.

The square root of 1661501665 is about 40761.5218680559. The cubic root of 1661501665 is about 1184.4050768162.

The spelling of 1661501665 in words is "one billion, six hundred sixty-one million, five hundred one thousand, six hundred sixty-five".