161561645 has 32 divisors (see below), whose sum is σ = 225662976. Its totient is φ = 108763200.

The previous prime is 161561623. The next prime is 161561663. The reversal of 161561645 is 546165161.

161561645 = 155² + 156² + ... + 787².

It is not a de Polignac number, because 161561645 - 2¹⁰ = 161560621 is a prime.

It is a super-3 number, since 3×161561645³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 765590 + ... + 765800.

It is an arithmetic number, because the mean of its divisors is an integer number (7051968).

Almost surely, 2^161561645 is an apocalyptic number.

It is an amenable number.

161561645 is a deficient number, since it is larger than the sum of its proper divisors (64101331).

161561645 is a wasteful number, since it uses less digits than its factorization.

161561645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521.

The product of its digits is 21600, while the sum is 35.

The square root of 161561645 is about 12710.6901858239. The cubic root of 161561645 is about 544.6440399273.

The spelling of 161561645 in words is "one hundred sixty-one million, five hundred sixty-one thousand, six hundred forty-five".