161639903 has 4 divisors (see below), whose sum is σ = 162802920. Its totient is φ = 160476888.

The previous prime is 161639899. The next prime is 161639957. The reversal of 161639903 is 309936161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 309936161 = 37 ⋅8376653.

It is a cyclic number.

It is not a de Polignac number, because 161639903 - 2² = 161639899 is a prime.

It is a super-2 number, since 2×161639903² = 52254916483698818, 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 (161639003) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 581300 + ... + 581577.

It is an arithmetic number, because the mean of its divisors is an integer number (40700730).

Almost surely, 2^161639903 is an apocalyptic number.

161639903 is a deficient number, since it is larger than the sum of its proper divisors (1163017).

161639903 is a wasteful number, since it uses less digits than its factorization.

161639903 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1163016.

The product of its (nonzero) digits is 26244, while the sum is 38.

The square root of 161639903 is about 12713.7682454888. The cubic root of 161639903 is about 544.7319648247.

The spelling of 161639903 in words is "one hundred sixty-one million, six hundred thirty-nine thousand, nine hundred three".