1661665566651 has 8 divisors (see below), whose sum is σ = 2215589956944. Its totient is φ = 1107759110400.

The previous prime is 1661665566641. The next prime is 1661665566677. The reversal of 1661665566651 is 1566655661661.

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

It is not a de Polignac number, because 1661665566651 - 2⁷ = 1661665566523 is a prime.

It is a super-2 number, since 2×1661665566651² (a number of 25 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1661665566611) 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, 4265806 + ... + 4639011.

It is an arithmetic number, because the mean of its divisors is an integer number (276948744618).

Almost surely, 2^{1661665566651} is an apocalyptic number.

1661665566651 is a deficient number, since it is larger than the sum of its proper divisors (553924390293).

1661665566651 is an equidigital number, since it uses as much as digits as its factorization.

1661665566651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8967021.

The product of its digits is 34992000, while the sum is 60.

The spelling of 1661665566651 in words is "one trillion, six hundred sixty-one billion, six hundred sixty-five million, five hundred sixty-six thousand, six hundred fifty-one".