161651845 has 4 divisors (see below), whose sum is σ = 193982220. Its totient is φ = 129321472.

The previous prime is 161651839. The next prime is 161651869. The reversal of 161651845 is 548156161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 548156161 = 7 ⋅78308023.

It can be written as a sum of positive squares in 2 ways, for example, as 117548964 + 44102881 = 10842^2 + 6641^2 .

It is a cyclic number.

It is not a de Polignac number, because 161651845 - 2⁷ = 161651717 is a prime.

It is a super-2 number, since 2×161651845² = 52262637983808050, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16165180 + ... + 16165189.

It is an arithmetic number, because the mean of its divisors is an integer number (48495555).

Almost surely, 2^161651845 is an apocalyptic number.

It is an amenable number.

161651845 is a deficient number, since it is larger than the sum of its proper divisors (32330375).

161651845 is an equidigital number, since it uses as much as digits as its factorization.

161651845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32330374.

The product of its digits is 28800, while the sum is 37.

The square root of 161651845 is about 12714.2378851428. The cubic root of 161651845 is about 544.7453794763.

The spelling of 161651845 in words is "one hundred sixty-one million, six hundred fifty-one thousand, eight hundred forty-five".