161990955361 has 9 divisors (see below), whose sum is σ = 162689839641. Its totient is φ = 161295065712.

The previous prime is 161990955349. The next prime is 161990955389. The reversal of 161990955361 is 163559099161.

The square root of 161990955361 is 402481.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 11571089761 + 150419865600 = 107569^2 + 387840^2 .

It is not a de Polignac number, because 161990955361 - 2¹³ = 161990947169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161990955311) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 111486511 + ... + 111487963.

It is an arithmetic number, because the mean of its divisors is an integer number (18076648849).

Almost surely, 2^161990955361 is an apocalyptic number.

161990955361 is the 402481-st square number.

161990955361 is the 201241-st centered octagonal number.

It is an amenable number.

161990955361 is a deficient number, since it is larger than the sum of its proper divisors (698884280).

161990955361 is an frugal number, since it uses more digits than its factorization.

161990955361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3460 (or 1730 counting only the distinct ones).

The product of its (nonzero) digits is 1968300, while the sum is 55.

The spelling of 161990955361 in words is "one hundred sixty-one billion, nine hundred ninety million, nine hundred fifty-five thousand, three hundred sixty-one".