161639993 has 4 divisors (see below), whose sum is σ = 161755008. Its totient is φ = 161524980.

The previous prime is 161639981. The next prime is 161640001. The reversal of 161639993 is 399936161.

161639993 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 399936161 = 59 ⋅6778579.

It is a cyclic number.

It is not a de Polignac number, because 161639993 - 2⁴ = 161639977 is a prime.

It is a super-2 number, since 2×161639993² = 52254974674080098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161632993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55373 + ... + 58218.

It is an arithmetic number, because the mean of its divisors is an integer number (40438752).

Almost surely, 2^161639993 is an apocalyptic number.

It is an amenable number.

161639993 is a deficient number, since it is larger than the sum of its proper divisors (115015).

161639993 is a wasteful number, since it uses less digits than its factorization.

161639993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115014.

The product of its digits is 236196, while the sum is 47.

The square root of 161639993 is about 12713.7717849582. The cubic root of 161639993 is about 544.7320659257.

The spelling of 161639993 in words is "one hundred sixty-one million, six hundred thirty-nine thousand, nine hundred ninety-three".