1625661209 has 4 divisors (see below), whose sum is σ = 1656334116. Its totient is φ = 1594988304.

The previous prime is 1625661203. The next prime is 1625661221. The reversal of 1625661209 is 9021665261.

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 957283600 + 668377609 = 30940^2 + 25853^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1625661209 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1625661203) 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, 15336374 + ... + 15336479.

It is an arithmetic number, because the mean of its divisors is an integer number (414083529).

Almost surely, 2^1625661209 is an apocalyptic number.

It is an amenable number.

1625661209 is a deficient number, since it is larger than the sum of its proper divisors (30672907).

1625661209 is an equidigital number, since it uses as much as digits as its factorization.

1625661209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30672906.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 1625661209 is about 40319.4891956731. The cubic root of 1625661209 is about 1175.8267810741.

The spelling of 1625661209 in words is "one billion, six hundred twenty-five million, six hundred sixty-one thousand, two hundred nine".