161636993905 has 64 divisors (see below), whose sum is σ = 218024654400. Its totient is φ = 114436833280.

The previous prime is 161636993893. The next prime is 161636993923. The reversal of 161636993905 is 509399636161.

It can be written as a sum of positive squares in 32 ways, for example, as 158581557729 + 3055436176 = 398223^2 + 55276^2 .

It is not a de Polignac number, because 161636993905 - 2¹⁵ = 161636961137 is a prime.

It is a super-2 number, since 2×161636993905² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 161636993905.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 78122211 + ... + 78124279.

It is an arithmetic number, because the mean of its divisors is an integer number (3406635225).

Almost surely, 2^161636993905 is an apocalyptic number.

It is an amenable number.

161636993905 is a deficient number, since it is larger than the sum of its proper divisors (56387660495).

161636993905 is a wasteful number, since it uses less digits than its factorization.

161636993905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2934.

The product of its (nonzero) digits is 7085880, while the sum is 58.

The spelling of 161636993905 in words is "one hundred sixty-one billion, six hundred thirty-six million, nine hundred ninety-three thousand, nine hundred five".