165209399 has 4 divisors (see below), whose sum is σ = 165286464. Its totient is φ = 165132336.

The previous prime is 165209357. The next prime is 165209431. The reversal of 165209399 is 993902561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 993902561 = 47 ⋅21146863.

It is a cyclic number.

It is not a de Polignac number, because 165209399 - 2¹⁶ = 165143863 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165206399) 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, 35222 + ... + 39635.

It is an arithmetic number, because the mean of its divisors is an integer number (41321616).

Almost surely, 2^165209399 is an apocalyptic number.

165209399 is a deficient number, since it is larger than the sum of its proper divisors (77065).

165209399 is an equidigital number, since it uses as much as digits as its factorization.

165209399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77064.

The product of its (nonzero) digits is 131220, while the sum is 44.

The square root of 165209399 is about 12853.3808392967. The cubic root of 165209399 is about 548.7125799899.

The spelling of 165209399 in words is "one hundred sixty-five million, two hundred nine thousand, three hundred ninety-nine".