161555501 has 4 divisors (see below), whose sum is σ = 164603772. Its totient is φ = 158507232.

The previous prime is 161555483. The next prime is 161555503. The reversal of 161555501 is 105555161.

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 110775625 + 50779876 = 10525^2 + 7126^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161555501 is a prime.

It is a super-2 number, since 2×161555501² = 52200359806722002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161555503) 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, 1524056 + ... + 1524161.

It is an arithmetic number, because the mean of its divisors is an integer number (41150943).

Almost surely, 2^161555501 is an apocalyptic number.

It is an amenable number.

161555501 is a deficient number, since it is larger than the sum of its proper divisors (3048271).

161555501 is an equidigital number, since it uses as much as digits as its factorization.

161555501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3048270.

The product of its (nonzero) digits is 3750, while the sum is 29.

The square root of 161555501 is about 12710.4484972010. The cubic root of 161555501 is about 544.6371357816.

The spelling of 161555501 in words is "one hundred sixty-one million, five hundred fifty-five thousand, five hundred one".