1661601121 has 4 divisors (see below), whose sum is σ = 1733844672. Its totient is φ = 1589357572.

The previous prime is 1661601119. The next prime is 1661601191. The reversal of 1661601121 is 1211061661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1661601121 - 2¹ = 1661601119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661601101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36121741 + ... + 36121786.

It is an arithmetic number, because the mean of its divisors is an integer number (433461168).

Almost surely, 2^1661601121 is an apocalyptic number.

It is an amenable number.

1661601121 is a deficient number, since it is larger than the sum of its proper divisors (72243551).

1661601121 is an equidigital number, since it uses as much as digits as its factorization.

1661601121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72243550.

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 1661601121 is about 40762.7418238764. The cubic root of 1661601121 is about 1184.4287088200.

Adding to 1661601121 its reverse (1211061661), we get a palindrome (2872662782).

It can be divided in two parts, 166160 and 1121, that added together give a square (167281 = 409²).

The spelling of 1661601121 in words is "one billion, six hundred sixty-one million, six hundred one thousand, one hundred twenty-one".