1645172321 has 8 divisors (see below), whose sum is σ = 1774151400. Its totient is φ = 1516540032.

The previous prime is 1645172261. The next prime is 1645172377. The reversal of 1645172321 is 1232715461.

It can be written as a sum of positive squares in 4 ways, for example, as 46771921 + 1598400400 = 6839^2 + 39980^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1645172321 - 2²⁶ = 1578063457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1645172381) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 76796 + ... + 95853.

It is an arithmetic number, because the mean of its divisors is an integer number (221768925).

Almost surely, 2^1645172321 is an apocalyptic number.

It is an amenable number.

1645172321 is a deficient number, since it is larger than the sum of its proper divisors (128979079).

1645172321 is a wasteful number, since it uses less digits than its factorization.

1645172321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173395.

The product of its digits is 10080, while the sum is 32.

The square root of 1645172321 is about 40560.7238717457. The cubic root of 1645172321 is about 1180.5121594125.

Adding to 1645172321 its reverse (1232715461), we get a palindrome (2877887782).

The spelling of 1645172321 in words is "one billion, six hundred forty-five million, one hundred seventy-two thousand, three hundred twenty-one".