161861639 has 4 divisors (see below), whose sum is σ = 161890056. Its totient is φ = 161833224.

The previous prime is 161861591. The next prime is 161861647. The reversal of 161861639 is 936168161.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 161861639 - 2¹² = 161857543 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 161861596 and 161861605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161861699) 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, 2384 + ... + 18149.

It is an arithmetic number, because the mean of its divisors is an integer number (40472514).

Almost surely, 2^161861639 is an apocalyptic number.

161861639 is a deficient number, since it is larger than the sum of its proper divisors (28417).

161861639 is an equidigital number, since it uses as much as digits as its factorization.

161861639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28416.

The product of its digits is 46656, while the sum is 41.

The square root of 161861639 is about 12722.4855669008. The cubic root of 161861639 is about 544.9809369647.

The spelling of 161861639 in words is "one hundred sixty-one million, eight hundred sixty-one thousand, six hundred thirty-nine".