161211861 has 6 divisors (see below), whose sum is σ = 232861590. Its totient is φ = 107474568.

The previous prime is 161211851. The next prime is 161211863. The reversal of 161211861 is 168112161.

It can be written as a sum of positive squares in only one way, i.e., 135140625 + 26071236 = 11625^2 + 5106^2 .

It is not a de Polignac number, because 161211861 - 2⁶ = 161211797 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161211863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8956206 + ... + 8956223.

It is an arithmetic number, because the mean of its divisors is an integer number (38810265).

Almost surely, 2^161211861 is an apocalyptic number.

It is an amenable number.

161211861 is a deficient number, since it is larger than the sum of its proper divisors (71649729).

161211861 is a wasteful number, since it uses less digits than its factorization.

161211861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17912435 (or 17912432 counting only the distinct ones).

The product of its digits is 576, while the sum is 27.

The square root of 161211861 is about 12696.9232887342. The cubic root of 161211861 is about 544.2507010653.

The spelling of 161211861 in words is "one hundred sixty-one million, two hundred eleven thousand, eight hundred sixty-one".