1661031187201 has 4 divisors (see below), whose sum is σ = 1661578121812. Its totient is φ = 1660484252592.

The previous prime is 1661031187199. The next prime is 1661031187331. The reversal of 1661031187201 is 1027811301661.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1576152191601 + 84878995600 = 1255449^2 + 291340^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661031187201 - 2¹ = 1661031187199 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661031187001) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 273462750 + ... + 273468823.

It is an arithmetic number, because the mean of its divisors is an integer number (415394530453).

Almost surely, 2^{1661031187201} is an apocalyptic number.

It is an amenable number.

1661031187201 is a deficient number, since it is larger than the sum of its proper divisors (546934611).

1661031187201 is an equidigital number, since it uses as much as digits as its factorization.

1661031187201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546934610.

The product of its (nonzero) digits is 12096, while the sum is 37.

Adding to 1661031187201 its reverse (1027811301661), we get a palindrome (2688842488862).

The spelling of 1661031187201 in words is "one trillion, six hundred sixty-one billion, thirty-one million, one hundred eighty-seven thousand, two hundred one".