1620165809 has 4 divisors (see below), whose sum is σ = 1621888500. Its totient is φ = 1618443120.

The previous prime is 1620165787. The next prime is 1620165817. The reversal of 1620165809 is 9085610261.

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

It can be written as a sum of positive squares in 2 ways, for example, as 967210000 + 652955809 = 31100^2 + 25553^2 .

It is a cyclic number.

It is not a de Polignac number, because 1620165809 - 2¹² = 1620161713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1620165829) 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, 859934 + ... + 861815.

It is an arithmetic number, because the mean of its divisors is an integer number (405472125).

Almost surely, 2^1620165809 is an apocalyptic number.

It is an amenable number.

1620165809 is a deficient number, since it is larger than the sum of its proper divisors (1722691).

1620165809 is an equidigital number, since it uses as much as digits as its factorization.

1620165809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1722690.

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 1620165809 is about 40251.2833211564. The cubic root of 1620165809 is about 1174.5003601373.

The spelling of 1620165809 in words is "one billion, six hundred twenty million, one hundred sixty-five thousand, eight hundred nine".