161985709 has 2 divisors, whose sum is σ = 161985710. Its totient is φ = 161985708.

The previous prime is 161985701. The next prime is 161985713. The reversal of 161985709 is 907589161.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 150062500 + 11923209 = 12250^2 + 3453^2 .

It is a cyclic number.

It is not a de Polignac number, because 161985709 - 2³ = 161985701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161985701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80992854 + 80992855.

It is an arithmetic number, because the mean of its divisors is an integer number (80992855).

Almost surely, 2^161985709 is an apocalyptic number.

It is an amenable number.

161985709 is a deficient number, since it is larger than the sum of its proper divisors (1).

161985709 is an equidigital number, since it uses as much as digits as its factorization.

161985709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 136080, while the sum is 46.

The square root of 161985709 is about 12727.3606454756. The cubic root of 161985709 is about 545.1201474583.

The spelling of 161985709 in words is "one hundred sixty-one million, nine hundred eighty-five thousand, seven hundred nine".