161601781 has 8 divisors (see below), whose sum is σ = 176387328. Its totient is φ = 146832000.

The previous prime is 161601761. The next prime is 161601809. The reversal of 161601781 is 187106161.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 161601781 - 2⁷ = 161601653 is a prime.

It is a super-2 number, since 2×161601781² = 52230271244743922, 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 (161601701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31036 + ... + 35866.

It is an arithmetic number, because the mean of its divisors is an integer number (22048416).

Almost surely, 2^161601781 is an apocalyptic number.

161601781 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

161601781 is a deficient number, since it is larger than the sum of its proper divisors (14785547).

161601781 is a wasteful number, since it uses less digits than its factorization.

161601781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7883.

The product of its (nonzero) digits is 2016, while the sum is 31.

The square root of 161601781 is about 12712.2689162871. The cubic root of 161601781 is about 544.6891373126.

The spelling of 161601781 in words is "one hundred sixty-one million, six hundred one thousand, seven hundred eighty-one".