161521739 has 4 divisors (see below), whose sum is σ = 163336680. Its totient is φ = 159706800.

The previous prime is 161521721. The next prime is 161521769. The reversal of 161521739 is 937125161.

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 161521739 - 2²⁰ = 160473163 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 161521699 and 161521708.

It is not an unprimeable number, because it can be changed into a prime (161521769) 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, 907337 + ... + 907514.

It is an arithmetic number, because the mean of its divisors is an integer number (40834170).

Almost surely, 2^161521739 is an apocalyptic number.

161521739 is a deficient number, since it is larger than the sum of its proper divisors (1814941).

161521739 is an equidigital number, since it uses as much as digits as its factorization.

161521739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1814940.

The product of its digits is 11340, while the sum is 35.

The square root of 161521739 is about 12709.1203078734. The cubic root of 161521739 is about 544.5991935679.

The spelling of 161521739 in words is "one hundred sixty-one million, five hundred twenty-one thousand, seven hundred thirty-nine".